Abstract
The control of gene expression at certain times during the mitotic cell division cycle is a common feature in eukaryotes. In fission yeast, at least five waves of gene expression have been described, with one transcribed at the M-G1 interval under the control of the PBF transcription factor complex. PBF consists of at least three transcription factors, two forkhead-like proteins Sep1p and Fkh2p, and a MADS box-like protein Mbx1p, and binds to PCB motifs found in the gene promoters. Mbx1p is under the direct control of the polo-like kinase Plo1p and the Cdc14p-like phosphatase Clp1p (Flp1p). Here, we show that M-G1 gene expression in fission yeast is also regulated by the anillin-like protein, Mid1p (Dmf1p). Mid1p binds in vivo to both Fkh2p and Sep1p, and to the promoter regions of M-G1 transcribed genes. Mid1p promoter binding is dependent on Fkh2p, Plo1p and Clp1p. The absence of mid1(+) in cells results in partial loss of M-G1 specific gene expression, suggesting that it has a negative role in controlling gene expression. This phenotype is exacerbated by also removing clp1(+), suggesting that Mid1p and Clp1p have overlapping functions in controlling transcription. As mid1(+) is itself expressed at M-G1, these observations offer a new mechanism whereby Mid1p contributes to controlling cell cycle-specific gene expression as part of a feedback loop.
Highlights
The process by which a cell duplicates and divides to produce two identical daughter cells is controlled by many different mechanisms
The genes are co-ordinately regulated by DNA sequence motifs called pombe cell cycle boxes (PCBs) found in the gene promoters, which are bound by a transcription complex, PCB binding factor (PBF)
Because the mid1+ gene is under PBF–PCB control, we examined whether Mid1p might have a role in regulating M–G1 gene expression
Summary
The process by which a cell duplicates and divides to produce two identical daughter cells is controlled by many different mechanisms Prominent amongst these is the specific regulation of gene expression, so that proteins required at particular cell cycle times are produced only when they are needed. Cell cycle-specific expression of each group is controlled by a combination of short, repeated DNA motifs found in the gene promoters to which a transcription factor complex binds. The genes are co-ordinately regulated by DNA sequence motifs called pombe cell cycle boxes (PCBs) found in the gene promoters, which are bound by a transcription complex, PCB binding factor (PBF). Related mechanisms appear to be operating in budding yeast and humans, suggesting that such processes are conserved and important (Darieva et al, 2006; Fu et al, 2008)
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