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  • br Author Contributions br Acknowledgments We thank Hiroyuki

    2022-01-14


    Author Contributions
    Acknowledgments We thank Hiroyuki Miyoshi, Makoto Nakanishi, Yoshikazu Johmura, Yuki Okada, Yoshinori Makino, Takashi Sutani, and Katsuhiko Shirahige for kindly providing materials and technical information, Shiho Takahashi-Kariyazono for technical advice, and all members of the Watanabe laboratory for their support and discussion. We also thank the National Bio-Resource Project of the MEXT, Japan, for yeast strains. This work was supported in part by JSPS Research Fellowship grant number 15J10950 (to Y.G.), JSPS KAKENHI grant number 24770180, 26440093 (to Y.T.), and MEXT KAKENHI grant number 25000014 (to Y.W.).
    Introduction Haspin (Haploid Germ Cell-specific Nuclear Protein Kinase) is a serine/threonine kinase that has been recently identified in mice (Tanaka et al., 1999). The reported Northern analysis of murine tissues found haspin mRNA only in testes and immunohistochemical analysis using an anti-haspin antiserum revealed that haspin protein was found in male germ cells, and its expression appeared greatest in haploid spermatids. The function of haspin invivo remains to be defined, but ectopically expressed haspin is localized to the nucleus, has DNA binding capacity, and leads to reduced cell proliferation when expressed in HEK-293 cells. It was therefore suggested that haspin plays a critical role in Dehydrocostus Lactone cessation and differentiation of haploid germ cells (Tanaka et al., 1999). The gene encoding murine haspin, Germcellspecificgene2 (Gsg2), has been localized to mouse chromosome 11, near the nitric oxide synthase 2 (Nos2) gene (Matsui et al., 1997). The location of the Gsg2/haspin gene is also very close to that determined for the murine integrin αE (Itgae) gene (Schön et al., 1999). I identified the human haspin gene during studies on the unexpected transcription of the integrin αE gene in tissues that do not express the αE (CD103) protein. Integrin αEβ7 is a heterodimeric adhesion molecule that binds to epithelial (E-) cadherin and is involved in retention of lymphocytes within the epithelium (Cepek et al., 1994, Karecla et al., 1995, Higgins et al., 1998, Schön et al., 1999). The human αE subunit cDNA was cloned from an intra-epithelial lymphocyte (IEL) cDNA library (Shaw et al., 1994). Northern analysis showed that the αE transcript is expressed at high levels in IEL and in tissues such as the small intestine, lung and thymus but is absent from many other locations including heart, skeletal muscle, liver, and kidney (Shaw et al., 1994). Integrin αEβ7 is also expressed on a sub-population of dendritic cells and on dendritic epidermal T cells in the mouse and rat (Kilshaw, 1993, Brenan and Rees, 1997), and on TGF-β treated murine mast cells (Smith et al., 1994). A recent report suggesting the presence of two αE genes in the rat (Brenan and Rees, 1997) prompted a search of the nucleotide sequence databases for evidence of two αE genes in humans or mice. No such evidence was found. Surprisingly however, many human αE-derived expressed sequence tags (ESTs) were derived from tissues where conventional αE is not expressed, such as heart, kidney and germ cells, and most murine αE ESTs are derived from testis. Here I describe a novel αE-derived transcript and show that it is abundantly expressed, particularly in testis. Characterization of the transcription initiation site of this RNA led to the discovery that it lies within 70 nucleotides of the beginning of the previously uncharacterized human haspin gene. The human and murine haspin genes are characterized, showing that the intronless gene for haspin is contained within an intron of the conventional integrin αE gene. Expression of haspin is not restricted to testis but is also found in diploid cells, suggesting that haspin has a wider role than previously assumed. Furthermore, haspin is a prototypical member of a new family of protein kinases with distinctive structural features.