MAL (mal, T-cell differentiation protein)

2010-07-01   Levent B Beder , Noboru Yamanaka 

Department of Otolaryngology Head, Neck Surgery, Wakayama Medical University, 811-1, Kimiidera, Wakayama, 641-8509, Japan




Atlas Image
Amplification of cDNA from different T-cell samples by PCR revealed that there are four different splicing variants of mRNA named as MAL-a (462 bp), MAL-b (333 bp), MAL-c (294 bp), and MAL-d (168 bp). These variants defined according to involvement of exon2 and/or exon3, while MAL-a includes all 4 exons. As the three introns were located between complete codons, the reading frame was maintained in all the transcripts. (Figure adapted from Atlas of Genetics and Cytogenetics in Oncology and Haematology).


Genomic DNA of MAL gene is located on chromosome 2q11.1 spans 21 kb and includes 4 exons interrupted by three introns.
The promoter lacks a consensus TATA box in the vicinity of transcription start side and there is no consensus polyadenylation signal, although ATAAAA sequence exists.
There are two separated promoter CpG islands at a totally 1500 bp length of region extending into the first intron and contains up to 116 CpG dinucleotides. CpG island is divided into two regions and usually methylation status of these regions are evaluated separately by specifically designed primer sets.
MAL promoter at 110 bp upstream of the transcriptional start site contains also several SP1 binding sites, which may be regulated by transcriptional activator SP1 (Tugores et al., 1997).


MAL coding sequence: bases 60-518, accession NM_002371.2.
The mRNA is 1051 bp and open reading frame is 460 bp in length. Translation begins from a start codon in exon 1, ends at a stop codon in exon 4, and results in a 153 amino acid protein product. mRNA orientation is forward and transcription occurs on plus strand. The first exon encodes the 5 untranslated region and the first 31 amino acids. The second and the third exons encode 56 and 42 amino acids, respectively. Fourth exon encodes the 24 amino acids at COOH-terminal and the 3 untranslated region. The intron boundaries follow the AG/GT rule of acceptor/donor splice signal sequences and splicing between exons occurs between the last nucleotide of a codon and the first one of the next codon (Rancano et al., 1994b).


There is no identified pseudogene.



MAL belongs to the MAL family of proteolipids including BENE, MAL2 and Plasmolipin. In mouse, the conserved motif of (Q/Y-G-W-V-M-F/Y-V), which is located at the junction of the first extracellular loop and the second membrane-associated domain serves as a fingerprint for the MAL family, although overall amino acid sequence identities between mouse MAL and the related proteins are between 29-37% (Magyar et al., 1997). This motif is also shared in human MAL family.
Molecular mass of the MAL protein is 16700 Da and assigned into proteolipid group based on the solubility feature in lipophilic solvents. MAL is a non-glycosylated integral membrane protein including four transmembrane domains as hydrophobic segments. Each of four exons encodes a hydrophobic membrane-associated segment and its adjacent hydrophilic sequence in the protein structure (Rancano et al., 1994a). A model is proposed about orientation of MAL protein in the membrane (Alonso et al., 1987).
Another feature of MAL is its transmembrane helices constituting the MARVEL (MAL and related proteins for vesicle trafficking and membrane link) domain. This domain is also found approximately in 20 open reading frames of human genome (Sanchez-Pulido et al., 2002). Furthermore, the domain is also found in the tight-junction-associated proteins including occluding, tricellulin, marvelD3 and in the synaptic-membrane-localized synaptophysin and synaptogyrin. Thus, a common characteristic of proteins containing the MARVEL domain is localization to specialized domains within surface membranes (Magal et al., 2009).


Alonso and Weissman originally identified MAL expression in intermediate and late stages of T-lymphocyte differentiation (Alonso and Weissman, 1987). Furthermore, expression of MAL mRNA is also found to be related with differentiation in urothelial cells, neuronal cells (Liebert et al., 1997; Wakeman et al., 1997) and esophageal epithelium (Mimori et al., 2007). Accordingly, expression is prominent in upper layers, while it is weak or absent in basal layers of esophageal epithelium (Marazuela et al., 2003). These results implied a strong relation between differentiation status and MAL expression.
Although four transcripts identified, MAL-a variant containing the all four exons is found to be the most abundantly expressed in several tissues including peripheral blood lymphocytes and HNSCC tissues (Rancano et al., 1994b; Beder et al., 2009).

Maruzela et al. defined a detailed expression status for MAL protein by immunostaining in a wide range of human tissues and expression is found to be mainly localized in epithelial cells, myelinating cells and T-lymphocytes (Marazuela et al., 2003). Detailed results according to this study:
A- MAL negative cells and tissues:
- Fibroblasts, endothelial cells, B lymphocytes, skeletal and smooth muscle, skin (keratinized squamous epithelium and subcutaneous fibro-adipose tissue).
B- MAL positive cells and tissues:
- Gastrointestinal tract: Epithelium in esophagus, stomach, ileum, colon, liver, and pancreas.
- Genitourinary tract: Multiple sites of tract including transitional epithelium of the urothelium.
- Respiratory tract: Ciliated columnar epithelium of bronchi and bronchioles, and type 2 pneumocytes of alveolae.
- Hematopoietic system: Expression is restricted to regions rich in T-cells including cortex of thymus and paracortical lymphocytes of lymph node and tonsil.
- Endocrine system: Thyroid follicular cells, medulla of adrenal gland.
- Nervous system: Axons of peripheral nerves and myelinating Schwann cells in peripheral nervous system, oligodendrocytes of white and gray matter in central nervous system.
- Exocrine glands: breast epithelium (Horne et al., 2009).


The MAL proteolipid is an integral membrane protein and generally embedded in the plasma membrane of epithelial cells (Magal et al., 2009). Expression is generally more pronounced in supranuclear - apical membrane domain for most of the polarized epithelia including gastrointestinal mucosa and thyroid follicular cells (Marazuela et al., 2003) according with its role in polarized sorting.
The protein has been mainly identified as an internal component of glycolipid-enriched membrane (GEM) domains in T-lymphocytes (Millan et al., 1997), in polarized epithelial MDCK cells (Zacchetti et al., 1995) and in myelin-forming cells (Kim et al., 1995). As intracellular placement, the protein is localized to endoplasmic reticulum of T-lymphocytes (Rancano et al., 1994b).


Plasma membrane (PM) of epithelial cells divided into apical membrane domain involved in exchange with the organ lumen, and the basolateral domain maintaining contact with neighboring cells and the underlying extracellular matrix. Localizing numerous PM proteins to apical and basolateral domains by direct or indirect pathways result in cell polarization. In the direct pathway, proteins delivered directly from the trans-golgi network (TGN) to the apical PM by raft-dependent or non-raft carriers. Rafts are clustering of glycospingolipids, sphingomyelin and cholesterol into membrane microdomains and therefore also named as GEM (glycosphingolipid- and cholestrol-enriched membrane) domains. These detergent insoluble membranes defined by resistancy to cold extraction with Triton X-100. Several proteins participate in structure of rafts.
MAL is an integral membrane component of raft domains and recycles between the Golgi complex and the apical membrane in MDCK cells (Puertollano et al., 1999a). Although, exact mechanism of MAL function in raft-dependent apical sorting is unknown, MAL family proteolipids are implicated to be potent regulator of apical transport by involving in the assembly and targeting of apical transport platforms and in the formation and stabilization of raft domains. Consensus sorting motifs in the C-terminus function in regulation of raft transport (Puertollano et al., 1997).
In apical sorting, PM proteins are clustered into either glycolipid raft domains or non-raft carriers. MAL and MAL2 together with FAPP2 take part in constitutive apical transport of Influenza hemagglutinin (HA) (Puertollano et al., 1999b) and GPI-anchored proteins (decay-accelerating F factor, folate receptor, GFP-GPI, 5-nucleotidase, CEA) by lipid-raft-associated mechanism (Weisz et al., 2009). Based on apical sorting of many proteins, MAL is implied to function in establishment of cell polarity, however, MAL knockout mice did not display a clear defect in neuronal and epithelial cell polarity (Harada, 2010).
Related with the location of MAL in membrane microdomains another role is also suggested in cell signaling (Alonso et al., 2001), although there is yet no clear evidence concerning this function.


MAL protein is shown to be widely conserved (94-97%) across species by sequence alignment. In MAL family of human, MAL displays 39% and 36% amino acid sequence identity with BENE and MAL2, respectively and all proteins have four-transmembrane domain structure.



Direct sequencing of the entire coding region revealed no somatic mutations in 20 cases of cervical cancers (Hatta et al., 2004) and in 24 head and neck cancer cell line series (Beder et al., 2009).
Currently, there is no further data in HGMD database.

Implicated in

Entity name
Various cancers
Diagnostic biomarker in cancer: Recent reports revealed that epigenetic silencing of MAL by hypermethylation may be a common event involved during initiation and progression of epithelial cancers. Based on specifically high hypermethylation of MAL promoter in various carcinomas including breast, cervix, colon and gastric cancers compared to normal epithelium, promoter methylation of the gene is suggested to be diagnostic marker for early detection of tumorigenesis (Buffart et al., 2008; Lind et al., 2008; Horne et al., 2009; Overmeer et al., 2009).
Tumor-metastasis suppressive vs oncogenic role: Current functions attributed to MAL gene does not reveal a clear mechanism for MAL in oncogenesis. The gene is suggested to have tumor suppressive role in some malignancies, while oncogenic role in others according with expression level in tumors and normal tissues.
In cervical carcinoma cell lines, MAL overexpression by transfection reduces proliferation rate and suppressed migration and anchorage-dependent growth. Furthermore, Fas-induced apoptosis is found to be related with reduced migration and tumorigenicity by ectopic expression of MAL in esophageal carcinoma (Mimori et al., 2003).
Entity name
Ovarian cancer
MAL mRNA is found to be the most differentially expressed gene between short and long-term survival groups by microarray study, and higher expression showed correlation with short survival (Berchuck et al., 2005).
Entity name
Esophageal carcinoma
MAL expression is severely down-regulated in esophageal carcinomas compared to normal epithelium (Mimori et al., 2003) and up-regulation of MAL expression induces differentiation in esophageal carcinoma cells (Mimori et al., 2007).
Entity name
Cervical carcinoma
MAL mRNA is found to be the most significantly down-regulated gene both in squamous cell carcinoma (SCC) and adenocarcinoma of cervix (Wilting et al., 2008). Ectopic expression of MAL in SiHa cells suppressed proliferation, migration, and anchorage-independent growth. Promoter methylation is also remarkably high in cervical malignancies and accordingly showed significant correlation with decreased expression. Interestingly, promoter methylation is also shown to be predictive for high-grade lesions of cervix i.e. severity of cervical disease (Overmeer et al., 2009).
Entity name
Colon carcinoma
Genome wide microarray analysis revealed MAL to be frequently hypermethylated in colon carcinoma cell lines correlating with down-regulation of mRNA expression (Mori et al., 2006). Another study confirmed these results in carcinoma tissues and defined promoter hypermethylation as 71% (45/63) and 80% (49/61) in colon adenomas and carcinomas, respectively, while it is rare in normal mucosa. Furthermore, protein expression were also absent in majority (198/231) colorectal carcinoma tissues in immunostaining (Lind et al., 2008). Based on these results, MAL methylation is suggested as a diagnostic marker for early colon carcinogenesis.
Entity name
Gastric cancer
Promoter hypermethylation located at the transcription start region is correlated with down-regulation of mRNA expression. Furthermore, methylation of this region is also significant related with a better survival (Buffart et al., 2008).
Entity name
Breast carcinoma
Tumor specific hypermethylation of the MAL promoter is found in 100% (6/6) of the breast cancer cell lines and 69% (25/36) of primary tumors. Ectopic expression of MAL in breast carcinoma cell lines reduced motility, while no effect was observed on cell cycle or growth. Absence of MAL protein expression was highly associated with poor disease-free survival in patients not received adjuvant chemotherapy (Horne et al., 2009).
Entity name
Head and neck squamous cell carcinoma (HNSCC)
In a review of DNA microarray analysis related with genetic expression profiles of HNSCC, MAL is found to be down-regulated in 10 out of the 26 studies (Choi et al., 2005). Interestingly, MAL expression is down-regulated in metastatic tumors of HNSCC including both cell lines derived from lymph node metastasis (65%) and metastatic tumor tissues (43%) compared to primary tumor counterparts. Furthermore, remarkable LOH (loss of heterozygosity) frequency (30%) is observed in primary tumor samples and metastatic tumors itself (Beder et al., 2009). These results suggest that loss of MAL expression may lead to metastasis in HNSCC.
Entity name
Like ovarian cancers, MAL overexpression is identified to be indicator for poor prognosis and disease outcome in patients with T cell lymphoma and Hodgkin lymphoma (Tracey et al., 2002; Hsi et al., 2006).


Pubmed IDLast YearTitleAuthors
117396282001The role of lipid rafts in signalling and membrane trafficking in T lymphocytes.Alonso MA et al
34942491987cDNA cloning and sequence of MAL, a hydrophobic protein associated with human T-cell differentiation.Alonso MA et al
194450222009T-lymphocyte maturation-associated protein gene as a candidate metastasis suppressor for head and neck squamous cell carcinomas.Beder LB et al
158975652005Patterns of gene expression that characterize long-term survival in advanced stage serous ovarian cancers.Berchuck A et al
190021702008MAL promoter hypermethylation as a novel prognostic marker in gastric cancer.Buffart TE et al
160921152005Genetic expression profiles and biologic pathway alterations in head and neck squamous cell carcinoma.Choi P et al
203568232010Molecular mechanism of polarized transport.Harada A et al
147180222004Down-regulation of members of glycolipid-enriched membrane raft gene family, MAL and BENE, in cervical squamous cell cancers.Hatta M et al
192087412009Inactivation of the MAL gene in breast cancer is a common event that predicts benefit from adjuvant chemotherapy.Horne HN et al
167073822006MAL is expressed in a subset of Hodgkin lymphoma and identifies a population of patients with poor prognosis.Hsi ED et al
85835101995Cloning and characterization of MVP17: a developmentally regulated myelin protein in oligodendrocytes.Kim T et al
90841361997Expression of mal is associated with urothelial differentiation in vitro: identification by differential display reverse-transcriptase polymerase chain reaction.Liebert M et al
183462692008Hypermethylated MAL gene - a silent marker of early colon tumorigenesis.Lind GE et al
195534702009Clustering and lateral concentration of raft lipids by the MAL protein.Magal LG et al
91681371997Myelin and lymphocyte protein (MAL/MVP17/VIP17) and plasmolipin are members of an extended gene family.Magyar JP et al
127042142003Expression of MAL, an integral protein component of the machinery for raft-mediated pical transport, in human epithelia.Marazuela M et al
90034261997The MAL proteolipid is a component of the detergent-insoluble membrane subdomains of human T-lymphocytes.Millán J et al
171517982007Loss of MAL expression in precancerous lesions of the esophagus.Mimori K et al
127761982003MAL gene expression in esophageal cancer suppresses motility, invasion and tumorigenicity and enhances apoptosis through the Fas pathway.Mimori K et al
169525492006A genome-wide search identifies epigenetic silencing of somatostatin, tachykinin-1, and 5 other genes in colon cancer.Mori Y et al
196626632009Repression of MAL tumour suppressor activity by promoter methylation during cervical carcinogenesis.Overmeer RM et al
101893741999The MAL proteolipid is necessary for normal apical transport and accurate sorting of the influenza virus hemagglutinin in Madin-Darby canine kidney cells.Puertollano R et al
81325411994Genomic structure and subcellular localization of MAL, a human T-cell-specific proteolipid protein.Rancaño C et al
124682232002MARVEL: a conserved domain involved in membrane apposition events.Sánchez-Pulido L et al
124145292002Identification of genes involved in resistance to interferon-alpha in cutaneous T-cell lymphoma.Tracey L et al
91156331997A tandem array of Sp-1 sites and a reverse initiator element are both required for synergistic transcriptional activation of the T-cell-specific MAL gene.Tugores A et al
94040041997MAL mRNA is induced during the differentiation of human embryonal carcinoma cells into neurons and is also localised within specific regions of the human brain.Wakeman JA et al
199232692009Apical trafficking in epithelial cells: signals, clusters and motors.Weisz OA et al
186187152008Integrated genomic and transcriptional profiling identifies chromosomal loci with altered gene expression in cervical cancer.Wilting SM et al
85497771995VIP17/MAL, a proteolipid in apical transport vesicles.Zacchetti D et al

Other Information

Locus ID:

NCBI: 4118
MIM: 188860
HGNC: 6817
Ensembl: ENSG00000172005


dbSNP: 4118
ClinVar: 4118
TCGA: ENSG00000172005


Gene IDTranscript IDUniprot

Expression (GTEx)



Pubmed IDYearTitleCitations
213890982011Combined promoter methylation analysis of CADM1 and MAL: an objective triage tool for high-risk human papillomavirus DNA-positive women.48
234569882013CADM1 and MAL promoter methylation levels in hrHPV-positive cervical scrapes increase proportional to degree and duration of underlying cervical disease.39
211901872011Combined CADM1 and MAL promoter methylation analysis to detect (pre-)malignant cervical lesions in high-risk HPV-positive women.37
154668892004Caveolin-1 and MAL are located on prostasomes secreted by the prostate cancer PC-3 cell line.34
259934782015The Myelin and Lymphocyte Protein MAL Is Required for Binding and Activity of Clostridium perfringens ε-Toxin.27
252817662014CADM1, MAL and miR124-2 methylation analysis in cervical scrapes to detect cervical and endometrial cancer.24
196421402010Elevated MAL expression is accompanied by promoter hypomethylation and platinum resistance in epithelial ovarian cancer.21
204005092010IRAK1 and IRAK4 promote phosphorylation, ubiquitination, and degradation of MyD88 adaptor-like (Mal).20
264824332015DNA hypermethylation and decreased mRNA expression of MAL, PRIMA1, PTGDR and SFRP1 in colorectal adenoma and cancer.20
194235402009Common variation in genes related to innate immunity and risk of adult glioma.19


Levent B Beder ; Noboru Yamanaka

MAL (mal, T-cell differentiation protein)

Atlas Genet Cytogenet Oncol Haematol. 2010-07-01

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