Chromosomal assignment and tissue distribution of novel expressed sequence tags from a human pancreatic islet cDNA library

Identification of sirm, a novel insulin-regulated SH3 binding protein that associates with Grb-2 and FYN

We have previously developed a mouse model of insulin-resistant diabetes by targeted inactivation of the insulin receptor gene. During studies of gene expression in livers of insulin receptor-deficient mice, we identified a novel cDNA, which we have termed sirm (Son of Insulin Receptor Mutant mice). sirm is largely, albeit not exclusively, expressed in insulin-responsive tissues. Insulin is a potent modulator of sirm expression, and sirm mRNA levels correlate with tissue sensitivity to insulin. The product of the sirm gene is a serine/threonine-rich protein with several proline-rich motifs and an NPNY motif, conforming to the consensus sequence recognized by the phosphotyrosine binding domains of insulin receptor substrate and Shc proteins. However, Sirm bears no extended homologies with other known proteins. Based on the sequences of the proline-rich domains, we sought to determine whether Sirm binds to the SH3 domains of FYN and Grb-2. We demonstrate here that Sirm binds to FYN and Grb-2 in 3T3-L1 adipocytes and that insulin treatment results in the dissociation of the Sirm.FYN and Sirm.Grb-2 complexes. We also show that Sirm is a substrate for the kinase activity of FYN in vitro. Based on the patterns of expression of sirm, its regulation by insulin, and the interactions with molecules in the insulin signaling pathway, we surmise that Sirm plays a role in modulating tissue sensitivity to insulin.

Construction of an integrated physical and gene map of human chromosome 20p12 providing candidate genes for Alagille syndrome

Physical mapping and localization of eSTS markers were used to generate an integrated physical and gene map covering a approximately 10-Mb region of human chromosome 20p12 containing the Alagille syndrome (AGS) locus. Seventy-four STSs, 28 of which were derived from cDNA sequences, mapped with an average resolution of 135 kb. The 28 eSTS markers define 20 genes. Six known genes, namely CHGB, BMP2, PLCB1, PLCB4, SNAP, and HJ1, were precisely mapped. Among the genes identified, one maps in the smallest region of overlap of the deletions associated with AGS and could therefore be regarded as a candidate gene for Alagille syndrome.

Identification and analysis of a functional human homolog of the SPT4 gene of Saccharomyces cerevisiae

Spt4p is a nonhistone protein of Saccharomyces cerevisiae that is believed to be required for normal chromatin structure and transcription. In this work we describe the isolation and analysis of a human gene, SUPT4H, that encodes a predicted protein 42% identical to Spt4p. When expressed in S. cerevisiae, SUPT4H complemented all spt4 mutant phenotypes. In human cells SUPT4H encodes a nuclear protein that is expressed in all tissues tested. In addition, hybridization analyses suggest that an SUPT4H-related gene is also present in mice. SUPT4H was localized to human chromosome 17 by PCR analysis of a human-rodent somatic cell hybrid panel. Thus, like other proteins that are components of or control the structure of chromatin, Spt4p appears to be conserved from S. cerevisiae to mammals.