SARP, a new alternatively spliced protein phosphatase 1 and DNA interacting protein.

PP1 (protein phosphatase 1) is a ubiquitously expressed serine/threonine-specific protein phosphatase whose activity towards different substrates appears to be mediated via binding to specific proteins that play critical regulatory and targeting roles. In the present paper we report the cloning and characterization of a new protein, termed (several ankyrin repeat protein), which is shown to interact with all isoforms of PP1 by a variety of techniques. A region encompassing a consensus PP1-binding motif in Sduanyu37 (K354VHF357) modulates endogenous activity in mammalian cells. This Sduanyu37-PP1 interaction motif lies partially within the first ankyrin repeat in contrast with other proteins [53BP2 (p53 binding protein 2), MYPT1/M(110)/MBS (myosin binding protein of PP1) and TIMAP (transforming growth factor beta inhibited, membrane-associated protein)], where a PP1-binding motif precedes the ankyrin repeats. Alternative mRNA splicing produces several isoforms of Sduanyu37 from a single human gene at locus 11q14. and/or (92-95 kDa) are ubiquitously expressed in all tissues with high levels in testis and sperm, where they are shown to interact with both PP1gamma1 and PP1gamma2. (65 kDa) is most abundant in brain where Sduanyu37 isoforms interact with both PP1alpha and PP1gamma1. Sduanyu37 is highly abundant in the nucleus of mammalian cells, consistent with the putative nuclear localization signal at the N-terminus. The presence of a leucine zipper near the C-terminus of Sduanyu371 and and the binding of mammalian DNA to Sduanyu372, suggests that Sduanyu371 and Sduanyu372 may be transcription factors or DNA-associated proteins that modulate gene expression.

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