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FUNCTION Recruited and tyrosine phosphorylated by several receptor systems, for example the T-cell, leptin and insulin receptors. Once phosphorylated, functions as an adapter protein in signal transduction cascades by binding to SH2 and SH3 domain-containing proteins. Role in G2-M progression in the cell cycle. Represses CBP-dependent transcriptional activation apparently by competing with other nuclear factors for binding to CBP. Also acts as a putative regulator of mRNA stability and/or translation rates and mediates mRNA nuclear export. Positively regulates the association of constitutive transport element (CTE)-containing mRNA with large polyribosomes and translation initiation. According to some authors, is not involved in the nucleocytoplasmic export of unspliced (CTE)-containing RNA species according to (PubMed:22253824). RNA-binding protein that plays a role in the regulation of alternative splicing and influences mRNA splice site selection and exon inclusion. Binds to RNA containing 5'-[AU]UAA-3' as a bipartite motif spaced by more than 15 nucleotides. Binds poly(A). Can regulate CD44 alternative splicing in a Ras pathway-dependent manner (PubMed:26080397). In cooperation with HNRNPA1 modulates alternative splicing of BCL2L1 by promoting splicing toward isoform Bcl-X(S), and of SMN1 (PubMed:17371836, PubMed:20186123). Can regulate alternative splicing of NRXN1 and NRXN3 in the laminin G-like domain 6 containing the evolutionary conserved neurexin alternative spliced segment 4 (AS4) involved in neurexin selective targeting to postsynaptic partners. In a neuronal activity-dependent manner cooperates synergistically with KHDRBS2/SLIM-1 in regulation of NRXN1 exon skipping at AS4. The cooperation with KHDRBS2/SLIM-1 is antagonistic for regulation of NXRN3 alternative splicing at AS4 (By similarity).FUNCTION Isoform 3, which is expressed in growth-arrested cells only, inhibits S phase.SUBUNIT Self-associates to form homooligomers when bound to RNA, oligomerization appears to be limited when binding to proteins; dimerization increases RNA affinity (PubMed:20610388, PubMed:26758068). Forms a trimeric complex in the nucleus consisting of BANP, HDAC6 and KHDRBS1/SAM68; HDAC6 keeps KHDRBS1 in a deacetylated state which inhibits the inclusion of CD44 alternate exons (PubMed:26080397). The complex is disrupted by MAPK1/MAPK3-mediated phosphorylation of BANP which results in BANP export to the cytoplasm (PubMed:26080397). This facilitates acetylation of KHDRBS1 and CD44 variant exon inclusion (PubMed:26080397). Interacts with KHDRBS3/SLIM-2 (PubMed:10332027). Interacts with KHDRBS2/SLIM-1; heterooligomer formation of KHDRBS family proteins may modulate RNA substrate specificity (By similarity). Interacts with RASA1, LCK, FYN, PTPN6, PLCG1, GRB2, CBL, JAK3, PIK3R, STAT3, APC, HNRNPA1 (PubMed:10332027, PubMed:11585385, PubMed:1374686, PubMed:17371836, PubMed:22000517, PubMed:9045636). Interacts with PTK6 (via SH3 and SH2 domains) (PubMed:10913193). Forms a complex with ILF2, ILF3, YLPM1, RBMX, NCOA5 and PPP1CA (PubMed:17890166). Does not interact with TPR (PubMed:22253824). Interacts with PRMT1 (By similarity). Binds WBP4/FBP21 (via WW domains), FNBP4/FBP30 (via WW domains). Interacts (via Arg/Gly-rich-flanked Pro-rich regions) with FYN (via the SH3 domain) (By similarity). Interacts with the non-receptor tyrosine kinase SRMS; the interaction leads to phosphorylation of KHDRBS1 (PubMed:29496907). Interacts with ZBTB7A; negatively regulates KHDRBS1 splicing activity toward BCL2L1 (PubMed:24514149).INTERACTION Predominantly located in the nucleus but also located partially in the cytoplasm.ALTERNATIVE PRODUCTS Ubiquitously expressed in all tissue examined. Isoform 1 is expressed at lower levels in brain, skeletal muscle, and liver whereas isoform 3 is intensified in skeletal muscle and in liver.DEVELOPMENTAL STAGE Isoform 3 is only expressed in growth-arrested cells.DOMAIN The KH domain is required for binding to RNA.DOMAIN The Pro-rich domains are flanked by Arg/Gly-rich motifs which can be asymmetric dimethylated on arginine residues to give the DMA/Gly-rich regions. Selective methylation on these motifs can modulate protein-protein interactions (By similarity).PTM Tyrosine phosphorylated by several non-receptor tyrosine kinases including LCK, FYN and JAK3. Also tyrosine phosphorylated by the non-receptor tyrosine kinase SRMS in an EGF-dependent manner (PubMed:29496907). Negatively correlates with ability to bind RNA but required for many interactions with proteins. Phosphorylation by PTK6 negatively regulates its RNA binding ability. Phosphorylation by PTK6 at Tyr-440 dictates the nuclear localization of KHDRBS1. Phosphorylation at Tyr-387 disrupts interaction with APC. Phosphorylation at tyrosine residues by FYN inverts activity on modulation of BCL2L1 alternative splicing.PTM Acetylated (PubMed:15021911, PubMed:26080397). Positively correlates with ability to bind RNA (PubMed:15021911). Deacetylated by HDAC6; this regulates alternative splicing by inhibiting the inclusion of CD44 alternate exons (PubMed:26080397).PTM Arginine methylation is required for nuclear localization. Also can affect interaction with other proteins. Inhibits interaction with Src-like SH3 domains, but not interaction with WW domains of WBP4/FBP21 and FNBP4/FBP30.SIMILARITY Belongs to the KHDRBS family.SEQUENCE CAUTION Intron retention.
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