The cAMP pathway in Schizosaccharomyces pombe is the major nutrient sensing pathway to initiate sexual development when opposite mating type cells exist. We identified moc1-moc4 as genes that overcome a partially sterile S. pombe strain due to an elevation of cAMP. When we compared the strength of inducing ability of sexual development in the same S. pombe strain, Moc1 had highest, Moc2 had lowest, and both Moc3 and Moc4 had intermediate effects. Moc1/Sds23 and Moc2/Ded1 are known to be a potential regulator of M-phase progression and an essential RNA helicase, respectively. While Moc4 was found to be identical with a Zn-finger protein Zfs1, Moc3 (SPAC821.07c) was a novel protein containing a Zn-finger (Zn(2)-Cys(6)) motif. Deletion mutant of the moc3 gene was constructed and its disruptant was found to be lower in mating efficiency and formed aberrant asci. In addition, unexpectedly, a moc3 disruptant was sensitive to CaCl(2) and DNA damaging agents such as MMS and UV. Those phenotypes were opposite to the phenotypes observed in a zfs1 disruptant, and quite different from the ones in a moc1 disruptant. Moc3 localized in the nucleus as observed for Zfs1. Moc3 bound with Moc4/Zfs1 weakly in the two hybrid system, but no other combination of Moc(s) bound each other in the same analysis. Thus, Moc3 is not only involved in sexual development, but also in ascus formation and DNA integrity in an independent manner with Moc1 and Moc2 in S. pombe.