Abstract: Disclosed is a purified full-length cDNA molecule encoding putative serine kinase enzyme (PSKH-1), and the expression of the cDNA in a recombinant host cell to produce substantially purified PSKH-1, per se. Inactivation of PSKH-1 pre-MRNA or PSKH-1 mRNA halts DNA synthesis and cell division. Also disclosed are ribozymes capable of cleaving PSKH-1 pre-mRNA or mRNA and thus deactivating PSKH-1 translation. Ribozymes of the hammerhead and hairpin motifs, and various compositions containing same, are also disclosed. The ribozymes compositions are used in the treatment of mammalian patients suffering from diseases or medical conditions characterized by abnormal cell proliferation or growth such as cancer and various non-malignant diseases or medical conditions such as autoimmune diseases, allograft rejection and atherosclerosis.