Expression and phosphorylation of the replication regulator protein geminin.
It has been described that the replication regulator protein geminin is rapidly degraded at the end of mitosis and newly expressed at the beginning of the next S phase in the metazoan cell cycle. We have performed experiments to investigate the synthesis of geminin in cycling human HeLa cells. The levels of geminin-mRNA vary only modestly during the cell cycle with a 2-3-fold higher mRNA level at the G1/S phase transition, whereas newly synthesized geminin can only be detected in post-G1 phases. Surprisingly, geminin, once synthesized, does not remain stable, but is turned over during S phase with a half-life of 3-4h. We also show that geminin becomes phosphorylated as S phase proceeds and identify by MALDI mass spectrometry two specific major phosphorylation sites.
Department of Biology, Universität Konstanz, D-78457, Konstanz, Germany. monika.kulartz@uni-konstanz.de
Monika
M
Kulartz
Sandra
S
Kreitz
Ekkehard
E
Hiller
Elena-Catalina
EC
Damoc
Michael
M
Przybylski
Rolf
R
Knippers
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D064248:Geminin; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D016196:S Phase; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; C577995:GMNN protein, human; D064248:Geminin; D012333:RNA, Messenger