RNA recognition motif 1 (RRM1) found in vertebrate matrin-3
This subgroup corresponds to the RRM1 of Matrin 3 (MATR3 or P130), a highly conserved inner nuclear matrix protein with a bipartite nuclear localization signal (NLS), two zinc finger domains predicted to bind DNA, and two RNA recognition motifs (RRM), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), that are known to interact with RNA. MATR3 has been implicated in various biological processes. It is involved in RNA processing by interacting with other nuclear proteins to anchor hyperedited RNAs to the nuclear matrix. It plays a role in mRNA stabilization through maintaining the stability of certain mRNA species. Besides, it modulates the activity of proximal promoters by binding to highly repetitive sequences of matrix/scaffold attachment region (MAR/SAR). The phosphorylation of MATR3 is assumed to cause neuronal death. It is phosphorylated by the protein kinase ATM, which activates the cellular response to double strand breaks in the DNA. Its phosphorylation by protein kinase A (PKA) is responsible for the activation of the N-methyl-d-aspartic acid (NMDA) receptor. Furthermore, MATR3 has been identified as both a Ca2+-dependent CaM-binding protein and a downstream substrate of caspases. Additional research indicates that matrin 3 also binds Rev/Rev responsive element (RRE)-containing viral RNA and functions as a cofactor that mediates the post-transcriptional regulation of HIV-1.