Mis17 is a regulatory module of the Mis6-Mal2-Sim4 centromere complex that is required for the recruitment of CenH3/CENP-A in fission yeast

The centromere is the chromosome domain on which the mitotic kinetochore forms for proper segregation. Deposition of the centromeric histone H3 (CenH3, CENP-A) is vital for the formation of centromere-specific chromatin. The Mis6-Mal2-Sim4 complex of the fission yeast S. pombe is required for the recruitment of CenH3 (Cnp1), but its function remains obscure. Mass spectrometry was performed on the proteins precipitated with Mis6- and Mis17-FLAG. The results together with the previously identified Sim4- and Mal2-TAP precipitated proteins indicated that the complex contains 12 subunits, Mis6, Sim4, Mal2, Mis15, Mis17, Cnl2, Fta1-4, Fta6-7, nine of which have human centromeric protein (CENP) counterparts. Domain dissection indicated that the carboxy-half of Mis17 is functional, while its amino-half is regulatory. Overproduction of the amino-half caused strong negative dominance, which led to massive chromosome missegregation and hypersensitivity to the histone deacetylase inhibitor TSA. Mis17 was hyperphosphorylated and overproduction-induced negative dominance was abolished in six kinase-deletion mutants, ssp2 (AMPK), ppk9 (AMPK), ppk15 (Yak1), ppk30 (Ark1), wis4 (Ssk2), and lsk1 (P-TEFb). Mis17 may be a regulatory module of the Mis6 complex. Negative dominance of the Mis17 fragment is exerted while the complex and CenH3 remain at the centromere, a result that differs from the mislocalization seen in the mis17-362 mutant. The known functions of the kinases suggest an unexpected link between Mis17 and control of the cortex actin, nutrition, and signal/transcription. Possible interpretations are discussed.