A NOVEL ESSENTIAL FISSION YEAST GENE PAD1(-DEPENDENT TRANSCRIPTION AND IS IMPLICATED IN THE MAINTENANCE OF CHROMOSOME STRUCTURE() POSITIVELY REGULATES PAP1(+))

Fission yeast pap1(+) gene encodes an AP-1-like transcription factor, whose overexpression can confer resistance to staurosporine, a protein kinase inhibitor. We have previously identified a target gene (p25) f or pap1(+), and shown that, crm1(+), which is required for maintenance of higher order chromosome structure, negatively regulates pap1-depen dent transcription, In this study, we have characterized a novel gene, pad1(+), which was isolated as a multicopy plasmid capable of conferi ng staurosporine-resistance. We shoved that high copy pad1(+) induces transcriptional activation of the p25 gene and that the induction by p ad1(+) is dependent on the pap1(+) gene, Furthermore, a cis-element an alysis of the 5'-region of the p25 gene showed that two elements (an A P-1 site and a 14 bp palindrome sequence) where pap1 binds in vitro is essential for the induction by pad1(+). These results indicate that p ad1 can positively regulate pap1-dependent transcription, Through an e lectromobility shift assay we showed that overexpression of pad1(+) is not capable of enhancing the DNA-binding activity of pap1 directly. T he pad1(+) gene encodes a 35 kDa protein that has significant identity (68%) to Caenorhabditis elegans F37A4.5, and is also similar to mouse Mov34 and human C6.1A. Gene disruption experiments have demonstrated that pad1(+) is essential for viability, A disruption mutant of pad1() obtained after spore germination exhibited an elongated cell body Ki th abberantly folded chromosomes. A mitotic plasmid loss experiment al so produced similar cells having an abnormal chromosome structure, The se suggest that pad1(+) may play an important role in higher order chr omosome structure, Taken concurrently with our previous results, two e ssential genes pad1(+) and crm1(+) regulate pap1-dependent transcripti on; pad1(+) and crm1(+) are positive and negative regulators, respecti vely.