The CDC16 gene is involved in the process of chromosome segregation in mitosis and a cdc16ts mutant accumulates the predominant microtubule-associated protein at the nonpermissive temperature. We find that the CDC16 gene open reading frame (ORF) is capable of encoding a protein whose calculated molecular weight and pI are 94,967 and 6.60, respectively. This hypothetical protein contains 16 cysteine residues; five are clustered at the N-terminal, 4 are placed about 3 residues apart in the middle of the peptide, and 3 are located close to the C-terminal. Each of these could form a metal-binding, nucleic acid-binding domain, suggesting this protein acts either as a repressor of the microtubule-associated protein gene or as a component necessary for spindle elongation, possibly interacting with the DNA. The start of the CDC16 ORF is only 95 bp downstream from the end of the MAK11 ORF. In this region there are two TATA boxes in tandem, but there is no room for a UAS or other regulatory sequences. An ATG is present 5 bp upstream of the start of the large ORF. Its frame terminates after only two amino acids.