| Note |
GeneLoc location for GC13M032575: Start: 32,575,307bp from pter; End: 32,757,892; Size: 182,585; Orientation: minus strand |
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| | Genomic characterization of human DLC2. (A) chromosomal map location of human DLC2 at 13q 12.3. Arrows underneath the gene symbols indicate the orientation of transcription. RFC3, replication factor C subunit 3; KL, Klotho; AS3, androgen shutoff 3; BRCA2, breast cancer 2, early onset; Tel, telomeric; Cen, centromeric. (B) genomic organization of human DLC2 locus. Non-coding (open boxes) and coding (filled boxes) are shown. (Ching YP,et al. J Biol Chem 2003) |
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| Description | DLC2 was identified due to striking sequence homology to DLC1. It localizes to a small region of 13q12.3, which is a locus frequently deleted in hepatocellular carcinoma (HCC) as well as in other cancers. Physical mapping of DLC2 in human genome revealed that it is in close proximity to the BRCA2 locus and flanked by microsatellite markers D13S171 and D13S267. The human DLC2 gene spans a region of 182 kb and contains 14 coding exons. |
| Transcription | The mRNA of DLC2 is 5886 bp long with an open reading frame of 3342 bp. Using bioinformatic analysis, 4 isoforms of DLC2, namely, DLC2alpha (5886 bp), DLC2beta (5810 bp), DLC2gamma (5784 bp), and DLC2delta (943 bp) have been identified. These 4 isoforms are generated by alternative splicing of the 5' end of the transcript. Northern blot analysis detected 7.2- and 4.2-kb DLC2 transcripts in all tissues examined, with the highest expression in heart, skeletal muscle, kidney, and pancreas. |
| Description | DLC2alpha encodes a 1113-amino acid protein which has a calculated molecular mass of 125 kD. DLC2 contains an N-terminal sterile alpha motif (SAM) domain for protein-protein interactions, followed by an ATP/GTP-binding motif, a GTPase-activating protein (GAP) domain, and a C-terminal STAR-related lipid transfer (START) domain. The 4 isoforms of DLC2, DLC2alpha, DLC2beta, DLC2gamma, and DLC2delta, encode proteins of 1113, 1105, 995, and 135 amino acids, respectively. DLC2alpha and DLC2beta encode a protein containing three functional domains, SAM, RhoGAP and START domains. DLC2alpha and DLC2beta differ by only a few N-terminal amino acids. DLC2gamma contains the RhoGAP and START domains, but lacks the N-terminal SAM domain, whereas DLC2delta contains only the SAM domain.
Co-immunoprecipitation assay of ectopically expressed DLC2 in cells revealed that DLC1 forms homodimers in vivo and the region 160-672 residues is responsible for the interaction. |
| Expression | DLC2 is ubiquitously expressed in human tissues and is more abundant in heart, skeletal muscle, kidney and pancreas. |
| Localisation | DLC2alpha, DLC2beta and DLC2gamma are predominantly localized in the cytoplasm in mouse fibroblast and human HCC cells. Cellular fractionation and immunofluorescence microscopy revealed that DLC2 localizes to cytoplasmic speckles overlapping with mitochondria and in structures in close proximity to lipid droplets. The START domain of DLC2 has been demonstrated to be responsible for mitochondria targeting of DLC2. |
| Function | DLC2 has been implicated to be a tumor suppressor protein. DLC2 has growth suppressive and anti-metastatic effects on HCC cell line, HepG2 and breast cancer cell line, MCF7. The RhoGAP domain has been demonstrated to be responsible for its biological functions and the RhoGAP activity has been demonstrated in vitro and in vivo. Recombinant DLC2 showed GAP activity specific for small GTPases, RhoA and Cdc42. Using GST-Rhoteckin pull down assay, in vivo RhoA activity has been shown to be negatively regulated by DLC2. However, in cells transfected with DLC2 RhoGAP mutant, the in vivo RhoA activity remained unchanged. Moreover, DLC2 inactivates RhoA activity via its RhoGAP domain and leads to the inhibition of actin stress fiber formation. Ectopic expression of DLC2 changed mouse fibroblast morphology from angular and spindle-shaped to round-shaped with dendritic cellular protrusions. Cells express DLC2 RhoGAP mutants did not exhibit morphological change and the actin stress fiber formation in these cells is unaffected. Introduction of human DLC2 into mouse fibroblasts suppressed Ras signaling and Ras-induced cellular transformation in a GAP-dependent manner. Overexpression of DLC2 also suppressed cell proliferation, motility and anchorage-independent growth in human hepatoma cells.
Collectively, down regulation of RhoA activity in HCC cell line by DLC2 resulted in change of cell morphology, migration rate, proliferation rate and transforming ability.
Several proteins were identified as interacting partners of DLC2 by yeast two-hybrid screening. These proteins include SWI/SNF, alpha-tubulin, HMG CoA reductase, and TAX1 binding protein (TAX1BP1). |
| Homology | DLC family members: DLC1 is located at chromosome 8p22; DLC3 is located at chromosome Xq13; DLC2 shares 51% and 52% amino acid identities with DLC1 and DLC3, respectively. |
| Deleted in liver cancer (DLC) 2 encodes a RhoGAP protein with growth suppressor function and is underexpressed in hepatocellular carcinoma. |
| Ching YP, Wong CM, Chan SF, Leung TH, Ng DC, Jin DY, Ng IO |
| The Journal of biological chemistry. 2003 ; 278 (12) : 10824-10830. |
| PMID 12531887 |
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| Chromosome 13q12 encoded Rho GTPase activating protein suppresses growth of breast carcinoma cells, and yeast two-hybrid screen shows its interaction with several proteins. |
| Nagaraja GM, Kandpal RP |
| Biochemical and biophysical research communications. 2004 ; 313 (3) : 654-665. |
| PMID 14697242 |
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| Rho GTPase activating protein cDNA on chromosome 13q12 is the deleted in liver cancer (DLC2) gene. |
| Popescu NC, Durkin ME |
| Biochemical and biophysical research communications. 2004 ; 315 (4) : page 781. |
| PMID 14985079 |
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| Deleted in liver cancer 2 (DLC2) suppresses cell transformation by means of inhibition of RhoA activity. |
| Leung TH, Ching YP, Yam JW, Wong CM, Yau TO, Jin DY, Ng IO |
| Proceedings of the National Academy of Sciences of the United States of America. 2005 ; 102 (42) : 15207-15212. |
| PMID 16217026 |
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| Mitochondrial targeting of growth suppressor protein DLC2 through the START domain. |
| Ng DC, Chan SF, Kok KH, Yam JW, Ching YP, Ng IO, Jin DY |
| FEBS letters. 2006 ; 580 (1) : 191-198. |
| PMID 16364308 |
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| Expression profile of the tumor suppressor genes DLC-1 and DLC-2 in solid tumors. |
| Ullmannova V, Popescu NC |
| International journal of oncology. 2006 ; 29 (5) : 1127-1132. |
| PMID 17016643 |
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| DLC-1:a Rho GTPase-activating protein and tumour suppressor. |
| Durkin ME, Yuan BZ, Zhou X, Zimonjic DB, Lowy DR, Thorgeirsson SS, Popescu NC |
| Journal of cellular and molecular medicine. 2007 ; 11 (5) : 1185-1207. |
| PMID 17979893 |
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| The NMR structure of the murine DLC2 SAM domain reveals a variant fold that is similar to a four-helix bundle. |
| Kwan JJ, Donaldson LW |
| BMC structural biology. 2007 ; 7 : page 34. |
| PMID 17519008 |
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| Solution structures, dynamics, and lipid-binding of the sterile alpha-motif domain of the deleted in liver cancer 2. |
| Li H, Fung KL, Jin DY, Chung SS, Ching YP, Ng IO, Sze KH, Ko BC, Sun H |
| Proteins. 2007 ; 67 (4) : 1154-1166. |
| PMID 17380510 |
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| Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities. |
| Qian X, Li G, Asmussen HK, Asnaghi L, Vass WC, Braverman R, Yamada KM, Popescu NC, Papageorge AG, Lowy DR |
| Proceedings of the National Academy of Sciences of the United States of America. 2007 ; 104 (21) : 9012-9017. |
| PMID 17517630 |
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