Inhibitor subunit of the major nuclear protein phosphatase-1 (PP-1). It has RNA-binding activity but does not cleave RNA and may target PP-1 to RNA-associated substrates. May also be involved in pre-mRNA splicing. Binds DNA and might act as a transcriptional repressor. Seems to be required for cell proliferation. Isoform Gamma is a site-specific single-strand endoribonuclease that cleaves single strand RNA 3' to purines and pyrimidines in A+U-rich regions. It generates 5'-phosphate termini at the site of cleavage. This isoform doesnot inhibit PP-1. May be implicated in mRNA splicing.Wang M., Proc. Natl. Acad. Sci. U.S.A. 91:10591-10595(1994).Van Eynde A., Eur. J. Biochem. 261:291-300(1999).Liu J.P., Submitted (FEB-1999) to the EMBL/GenBank/DDBJ databases.