Cyclic AMP regulates the expression and nuclear translocation of RFC40 in MCF7 cells.
We have previously shown that the regulatory subunit of PKA, RIalpha, functions as a nuclear transport protein for the second subunit of the replication factor C complex, RFC40, and that this transport appears to be crucial for cell cycle progression from G1 to S phase. In this study, we found that N(6)-monobutyryl cAMP significantly up-regulates the expression of RFC40 mRNA by 1.8-fold and its endogenous protein by 2.3-fold with a subsequent increase in the RIalpha-RFC40 complex formation by 3.2-fold. Additionally, the nuclear to cytoplasmic ratio of RFC40 increased by 26% followed by a parallel increase in the percentage of S phase cells by 33%. However, there was reduction in the percentage of G1 cells by 16% and G2/M cells by 43% with a concurrent accumulation of cells in S phase. Interestingly, the higher percentage of S phase cells did not correlate with a parallel increase in DNA replication. Moreover, although cAMP did not affect the expression of the other RFC subunits, there was a significant decrease in the RFC40-37 complex formation by 81.3%, substantiating the decrease in DNA replication rate. Taken together, these findings suggest that cAMP functions as an upstream modulator that regulates the expression and nuclear translocation of RFC40.
Gupte
Rakhee S
RS
Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA.
Sampson
Valerie
V
Traganos
Frank
F
Darzynkiewicz
Zbigniew
Z
Lee
Marietta Y W T
MY
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology / Q000502:physiology*; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000187:drug effects / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006801:Humans; D051818:Replication Protein C / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects; D014158:Transcription, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; C497561:RFC2 protein, human; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D051818:Replication Protein C