Non-histone protein associated with centromeric heterochromatin in the mouse chromosome

Distribution of protein in cytological preparations of the mouse metaphase chromosome was studied using protein-specific fluorochroming with dansyl chloride. Dansyl-fluorescence was relatively uniform along the axis of untreated chromosomes. After treatment of air-dried chromosome preparations with 0.2 N HCl, dansyl-fluorescence in chromosomes was remarkably reduced; it exhibited, however, bright fluorescent blocks at centromeric regions in almost all chromosomes. The same situation was observed in the male meiotic chromosomes at diakinesis; the Y chromosome seemed to lack bright dansyl-fluorescent block at the centromere after 0.2 N HCl extraction. The bright dansyl-fluorescent blocks in chromosomes after HCl or NaCl treatment occupied the same regions as C-bands. These observations suggested that centromeric constitutive heterochromatin in the mouse chromosome was associated with particular non-histone protein.