title: BAD/BCL-[X(L)] heterodimerization leads to bypass of G0/G1 arrest.
abstract: The pro-apoptotic molecule BAD binds BCL-[X(L)] or BCL2 and inactivates their survival function. In addition to their anti-apoptotic function, BCL2 and BCL-[X(L)] also delay cell cycle entry from quiescence. We found that the BH3-only molecule BAD also exerted a cell cycle effect. BAD expression resulted in failure to cell cycle block in growth arrest conditions. In low serum and in confluence, fibroblasts constitutively or inducibly expressing BAD persisted in S phase, continued to incorporate BrdU, and exhibited sustained cyclin E/cdk2 activity. Mutation analysis indicated that the cell cycle effect of BAD was not dependent on its phosphorylation status or subcellular localization, but strictly co-segregated with BCL-[X(L)] binding. bclx(-/-) MEFs expressing BAD and bad(-/-) MEFs both arrested in G0/G1 in low serum similar to wild-type controls, suggesting that the ability to overcome the G0/G1 checkpoint resulted from the presence of BAD/BCL-x(L) heterodimers, rather than the absence of BCL-[X(L)] or BAD. These data provide evidence that in addition to regulating apoptosis, the BAD/BCL-[X(L)] heterodimer has a novel cell cycle function.
authors.affiliation: Department of Pediatrics, Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: A
authors.initials: A
authors.lastname: Chattopadhyay
authors.forename: C W
authors.initials: CW
authors.lastname: Chiang
authors.forename: E
authors.initials: E
authors.lastname: Yang
mesh_terms: D000818:Animals; D017209:Apoptosis; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002455:Cell Division; D002478:Cells, Cultured; D003260:Contact Inhibition; D016895:Culture Media, Serum-Free; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004261:DNA Replication; D019281:Dimerization; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology*; D010766:Phosphorylation; D011487:Protein Conformation; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D016192:Resting Phase, Cell Cycle / Q000502:physiology*; D013329:Structure-Activity Relationship; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
chemical_list: C494821:Bad protein, rat; C494813:Bcl2l1 protein, rat; D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases