Cloning and characterization of human haspin gene encoding haploid germ cell-specific nuclear protein kinase.

We report here the molecular cloning and characterization of human haspin cDNA and its genomic DNA construct. The haspin protein is a unique protein kinase, first isolated from mouse testis. Specifically expressed in mouse testicular germ cells, haspin is suggested to play a role in cell cycle arrest in haploid spermatids. Detection of human haspin by Northern blot analysis showed that the major transcript was 2.8 kilobases long and detected exclusively in the testis. The entire coding region of the human cDNA showed 68% identity with mouse haspin. The predicted amino acid sequence showed strong conservation of the kinase catalytic domain, leucine zipper, potential phosphorylation sites, and MEF2B homologous region, but a relatively unique N-terminal region. Human haspin protein was also demonstrated to have protein kinase activity. The human haspin gene was mapped to chromosome 17p13 by computer database cloning of human genomic DNA. Furthermore, the genomic structure of human haspin was proven to be intronless and the whole transcription unit was found to be located in an intron of the integrin αE2 gene.