The RhoA gene can be found on chromosome 3 at location: 49371585-49424530. This gene includes 5 exons.

This gene has 6 transcripts (splice variants): 2031 bp (variant a); 961 bp (variant b); 889 bp (variant c); 633 bp (variant d); 539 bp (variant e); 388 bp (variant f).

The RhoA protein encodes five alternative isoforms: variant a (193 amino acids), variant b (187 amino acids), variant c (90 amino acids), variant d (129 amino acids) and variant e (86 amino acids).
- RhoA structure:
The available functional and structural data show that RHO-GTP-binding proteins are made-up of an effector domain, four separate guanosine phosphate binding regions that span the length of the core structure, a hypervariable region and a CAAX box motif (C: Cys; A: aliphatic residue; X: any residue). The effector domain (residues 26-45) changes conformation between the GTP bound and GDP bound states. All RHO proteins have conserved residues at Gly14, Thr19, Phe30 and Gln93 which are involved in binding, stabilization or regulation of GTP hydrolysis. The N-terminus region also contains switch 1 (residues 27-40) and switch 2 (residues 59-78) regions which change conformation between GTP- and GDP-bound states and may facilitate changes in effector region required for binding to downstream targets. RhoA protein is target for several bacterial toxins, which modify key conserved amino acids involved in their regulation. These include Clostridium botulinum exoenzyme C3 transferase, which modifies Asn41, and Toxin B, which acts on Thr37. The hypervariable region made-up of residues 173-189 is the region of most diversity between individual RHO family members. It may contain sites for palmitoylation and a polybasic region which can determine membrane association. The C-terminus of RhoA is essential for correct localization of the protein. RhoA is post-translationally modified by prenylation of a conserved C-terminal cysteine followed by methylation and proteolytic removal of the last three amino acids. The prenyl group (geranylgeranyl) anchors the GTPase into membranes and this modification is essential for its stability, cell growth, transformation, and cytoskeletal organization.
- RhoA activity regulation:
Rho GTPases can be activated by intrinsic or extrinsic cues, setting off a signaling cascade (Etienne-Manneville and Hall, 2002). Rho GTPases behave as molecular switches that fluctuate between inactive and active states, two conformations that depend on the binding of either GDP or GTP to the GTPases, respectively (Bustelo et al., 2007). Two types of regulatory proteins control this cycling: guanine nucleotide-exchange factors (GEFs), which activate Rho GTPases by catalyzing the exchange of GDP for GTP (Rossman et al., 2005), and GTPase-activating proteins (GAPs), which inactivate the GTPases by enhancing intrinsic GTP hydrolysis activity (Bos et al., 2007). There are over 80 GEFs and 70 GAPs for Rho GTPases, whose activity is tightly regulated and can be highly specific. RhoA can be sequestered in the cytoplasm by guanine nucleotide-dissociation inhibitors (GDIs), which bind prenylated GDP-bound Rho proteins (Garcia-Mata et al., 2011), allowing translocation of Rho GTPases between membranes and cytosol.
- RhoA effectors binding:
To date, at least 21 proteins have been identified which directly interact with RhoA (ROCK1, ROCK2, PRKcA, PKN1, PKN2, RTKN1, RTKN2, RHPN1, RHPN2, KTN1, CIT, DIAPH1, KCNA2, ITRP1, PLD, MYBPH, PIP5K, FAK, BORG, MBS, GDIA). Some of these have been shown to contribute to specific responses downstream of RhoA. Similarly to GEFs and GAPs, effectors bind to Rho both through the Switch 1 and 2 regions, but the amino acids involved in interaction with each target differ.

RhoA protein is expressed in all tissues tested. RhoA expression in normal human tissues, embryonic tissues and stem cells.

RhoA localizes predominantly in the plasmatic membrane and cytoplasm. Also, it localizes to cell-cell contacts and cell projections.

RhoA is a protein involved in multiple cellular processes.
- Role in actin organization:
RhoA protein plays a central role in regulating cell shape, polarity and locomotion through their effects on actin polymerization, actomyosin contractility, cell adhesion, and microtubule dynamics. RhoA is believed to act primarily at the rear of migrating cells to promote detachment.
RhoA directly stimulates actin polymerization through activiation of diaphanous-related formins (DRFs, also known as Dia proteins). These stimulate addition of actin monomers to the fast-growing end of actin filaments. DRFs act together with ROCKs to mediate Rho-induced stress fiber formation. ROCK-mediated phosphorylation of LIMK and consequent inhibition of cofilin also contributes to the increase in actin filaments in response to Rho. In addition, ROCKs induce actomyosin-based contractility and phosphorylate several proteins involved in regulating myosins and other actin-binding proteins. Actomyosin contractility is important in migrating cells for detachment of the rear. Microtubules are essential for determining cell polarity as well as for vesicular locomotion and intracellular transport. The concerted action of ROCK and Dia is essential for the regulation of cell polarity and organization of microtubules. ROCK phosphorylates TAU and MAP2, proteins that regulate microtubule stability.
RhoA plays a key role in regulating the integrity of cell-extracellular matrix and cell-cell adhesions, the latter including both adherens junctions and tight junctions. Loss of cell-cell junctions is required form the migration of epithelial cells and may be regulated reciprocally by ROCKs and DRFs. Also, RhoA is localized to developing axons and growth cones, and this localization is mediated by an axonal targeting element located in the RhoA 3 untranslated region (UTR). Local RhoA translations regulates the neuronal cytoskeleton and identify a new mechanism for the regulation of RhoA signaling (Wu et al., 2005). On the other hand, increasing expression of the transcription repressor, GCF2, can silence RhoA expression, leading to actin cytoskeleton disorganization (Shen et al., 2012).
- Role in cell migration:
The inhibition of RhoA signaling by blocking the interaction with its downstream effectors Rho-associated kinase (ROCK) and mDia is required for both vaccinia morphogenesis and virus-induced cell motility (Valderrama et al., 2006).
- Role in cell protrusion:
RhoA activates focal adhesion kinase (FAK) signaling. RhoA has a role in the initial events of protrusion, whereas Rac1 and Cdc42 activate pathways implicated in reinforcement and stabilization of newly expanded protrusions (Machacek et al., 2009).
- Role in exocytosis:
RhoA is involved in Ca²⁺-dependent exocytosis at least partly through the reorganization of actin filaments (Komuro et al., 1996). This type of exocytosis is regulated by G12/G13 alpha through a Rho/Rho-associated kinase-dependent pathway (Yamaguchi et al., 2000).
- Role in endocytosis:
RhoA helps direct endocytosis in a variety of cell types (Lamaze et al., 1996; Khandelwal et al., 2010; Yu et al., 2010). RhoA is essential for clathrin- and caveolar- independent endocytosis (Sabharanjak et al., 2002). Treatment with the PI3K inhibitor (LY294002) or the FAK inhibitor (PF573228) suppresses compensatory endocytosis by inhibiting the activation of RhoA and then reducing the recruitment of ROCK (Khandelwal et al., 2010).
- Role in cytokinesis:
Cytokinesis requires actomyosin-based contraction. Inhibition of ROCK or citron kinase causes defects in cytokinesis resulting in multinucleate cells. Diaphanous-related formins (DRFs) are also implicated in this process, the DRF mDia1 localizes to the cleavage furrow during cytokinesis. DRFs could contribute to cytokinesis by stimulating local actin polymerization and/or by coordinating microtubules with actin filaments at the site of the contractile ring. RhoA signaling is controlled by the central spindle, a set of microtubule bundles that forms between the separating chromosomes. Thus, inactivation of Rac by centralspindlin functions in parallel with RhoA activation to drive contractile ring constriction during cytokinesis (Canman et al., 2008).
- Role in cell cycle regulation:
RhoA plays a pivotal role in G1 cell cycle progression, primarily through regulation of both cyclin D1 expression, and the levels of the cyclin-dependent kinase inhibitors p21 and p27. Multiple pathways seem to link Rho proteins to the control of cyclin D1 levels. Many of these involve the activation of protein kinases, leading to the subsequent modulation of transcription factor activity. RhoA suppresses p21 levels in multiple normal and transformed cell lines. This effect appears to occur through a transcriptional mechanism but is independent of p53, a major transcriptional regulator of p21. RhoA plays an important role in determining the levels of p27 through a pathway involving its effector, the Rho-associated kinases. RhoA facilitates entry into S phase by degradation of the cyclin-dependent kinase inhibitor p27kip1 (Hirai et al., 1997).
- Role in development:
RhoA protein is required for processes involving cell migration in development including: neurite outgrowth, dorsal closure, bone formation, and myogenesis. Rho-loss of function is embryonically lethal in mouse development by E7. This is attributed to failure in gastrulation and an inability of cells to migrate.
- Role in transcriptional control:
The relationship between many of the cellular functions mediated by RhoA with transcriptional regulation has been described. RhoA modulates the activity of SRF, NF-kappaB, c/EBPb, Stat3, Stat5, FHL-2, PAX6, GATA-4, E2F, estrogen receptor alpha, estrogen receptor beta, CREB, and transcription factors that depend on the JNK and p38 MAP kinase pathways. Substrates to these kinases include c-Jun, ELK, PEA3, ATF2, MEF2A, Max and CHOP/GADD153.
- Role in cell proliferation:
RhoA plays cell type-specific roles in the regulation of cell proliferation. RhoA plays critical roles in both early and late stages of B-cell development (Zhang et al., 2012).

48 mutations have been described in the RhoA gene, according to the Catalogue of Somatic Mutations in Cancer (COSMIC) database.
De novo mutations have been described in patients with Burkitt lymphoma: R5Q and I23R (Richter et al., 2012; Rohde et al., 2014); peripheral T-cell lymphoma: G17V, affecting the GTP-binding domain (Manso et al., 2014; Palomero et al., 2014; Sakata-Yanagimoto et al., 2014; Yoo et al., 2014); head and neck carcinoma: E40Q and Y42I, affecting the effector domain (Lawrence et al., 2014); diffuse-type gastric carcinoma: R5Q, Y42I and G17V (Kakiuchi et al., 2014).