EXPRESSION, NUCLEAR-LOCALIZATION AND INTERACTIONS OF HUMAN MCM P1 PROTEINS/

We report here the comparative analysis of human Mcm/P1 proteins (HsMc m2, -3, -5 and -7), including a characterization of their mutual inter actions, cell cycle dependent expression and nuclear localization duri ng the cell cycle and the quiescent state. The mRNA levels of these ge nes, which undergo cell cycle dependent oscillations with a peak at G1 /S phase, may be regulated by E2F motifs, two of which were detected i n the 5' upstream region of the HsMCM5 gene, In contrast, the protein levels of these Mcm proteins were found to remain rather constant duri ng the HeLa cell cycle, However, their levels gradually increased in a variable manner as KD cells progressed from G0 into the G1/S phase, I n the G0 stage, the amounts of HsMcm2 and -5 proteins were much lower than those of HsMcm7 and -3 proteins, suggesting that they are not pre sent in stoichiometric amounts, and that only a proportion of these mo lecules actively participate in cell cycle regulation as part of Mcm/P 1 complexes. (C) 1997 Academic Press.