Sak kinase gene structure and transcriptional regulation

The Sak gene encodes a serine/threonine kinase, which is a member of the Po lo family of mitotic regulators. Sak transcripts are present in S/G2/M phas e cells, and in proliferating cell layers of the mouse embryo and adult tis sues. In this report, we have characterized the murine Sak gene structure, the Sak chromosomal location, and identified the promoter. The murine Sak g ene is located on the proximal arm of mouse chromosome 13, as determined by RFLP analysis. The murine gene comprises 15 coding exons spanning 16 kb of genomic sequence, and encodes two alternately spliced transcripts. Sak-a, the predominant transcript, is encoded by 15 exons, while early termination of transcription and alternative splicing at exons 5 and 6 results in Sak- b. This truncated transcript encodes the complete kinase domain and a carbo xyl end translated from 147 bp of sequence contiguous with exon 5. Human Sa k-a (Stk18) cDNA is reported to contain an insertion of sequence correspond ing to the mouse Sak-b tail. Primer extension analysis of murine Sak reveal ed one major transcription start site at position -303 bp relative to the s tart of translation. A genomic fragment of 3.5 kb located 5' of the Sak tra nscriptional start drives expression of a luciferase-reporter gene in CHO a nd GC1-SPG cells in an orientation-dependent fashion. Using various Sak pro moter/luciferase constructs, the core promoter region required for expressi on was located within 400 bp of the message Cap site, and sequence further 5' strongly suppressed transcription. (C) 2000 Elsevier Science B.V. All ri ghts reserved.