The kin28 protein kinase is associated with a cyclin in Saccharomyces cerevisiae.

Kin28 is an essential serine-threonine kinase of Saccharomyces cerevisiae. Multicopies of a novel cyclin gene, CCL1, are able to suppress the thermosensitivity of two kin28-ts mutants. The CCL1 gene is not cyclically transcribed, yet its product is also essential for cell proliferation. Furthermore, when overexpressed under high expression promoter, Cell is able to replace G1 function of Cln cyclins. Cell and Kin28 are physically associated in vivo. Therefore, like p34CDC28/cdc2, Kin28 may be a cyclin dependent kinase which is required for cell proliferation.