FUS-interacting serine-arginine-rich protein 1 is a protein that in humans is encoded by the SFRS13A gene.

This gene product is a member of the serine-arginine (SR) family of proteins, which is involved in constitutive and regulated RNA splicing. Members of this family are characterized by N-terminal RNP1 and RNP2 motifs, which are required for binding to RNA, and multiple C-terminal SR/RS repeats, which are important in mediating association with other cellular proteins. This protein can influence splice site selection of adenovirus E1A pre-mRNA. It interacts with the oncoprotein TLS, and abrogates the influence of TLS on E1A pre-mRNA splicing. This gene has multiple pseudogenes. Alternative splicing of this gene results in multiple transcript variants encoding different isoforms. In addition, transcript variants utilizing alternative polyA sites exist.[provided by RefSeq, Jul 2010].
Function: Splicing factor that in its dephosphorylated form acts as a general repressor of pre-mRNA splicing. Seems to interfere with the U1 snRNP 5'-splice recognition of SNRNP70. Required for splicing repression in M-phase cells and after heat shock. May be involved in regulation of alternative splicing in neurons, with isoform 1 acting as a positive and isoform 3 as a negative regulator.