Ser727/Tyr701-phosphorylated Stat1 is required for the regulation of c-Myc, cyclins, and p27Kip1 associated with ATRA-induced G0/G1 arrest of U-937 cells.
All-trans retinoic acid (ATRA)-induced growth arrest of myeloid cells is associated with a sequential regulation of cyclins and cyclin-dependent kinase inhibitors (CKIs), which modulates the cell cycle machinery and inhibits the G1-S phase progression. ATRA treatment of myeloid cells induces up-regulation and tyrosine phosphorylation of Stat1, a member of the STAT (signal transducer and activator of transcription) transcription factor family that has been implicated in growth arrest in response to interferons. We have previously shown that ATRA-induced cell cycle arrest is dependent on tyrosinephosphorylated Stat1. In this study, we show that there is a basal level of Stat1 Ser727 phosphorylation in U-937 cells, which is transiently increased in response to ATRA treatment. Using Stat1Ser727Ala-expressing sublines, we provide evidence that Ser727 phosphorylation of Stat1 is required for ATRA-induced growth arrest. To shed further light on the role of Stat1 in ATRA-induced cell cycle arrest, cyclin and CKI expression was analyzed during ATRA treatment in U-937 sublines expressing Stat1Ser727Ala and Stat1Tyr701Phe. Our results show that Ser727/Tyr701-phosphorylated Stat1 plays a key role as a prerequisite for the ATRA-induced down-regulation of c-Myc; cyclins A, B, D2, D3, and E; and the simultaneous up-regulation of p27Kip1, associated with arrest in the G0/G1 phase of the cell cycle.
Dimberg
Anna
A
Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, S-751 85 Uppsala, Sweden.
Karlberg
Inger
I
Nilsson
Kenneth
K
Oberg
Fredrik
F
D018797:Cell Cycle Proteins / Q000235:genetics; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D007399:Interphase / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D050794:STAT1 Transcription Factor; D012694:Serine / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism* / Q000502:physiology*; D014212:Tretinoin / Q000494:pharmacology*; D025521:Tumor Suppressor Proteins / Q000235:genetics; D014443:Tyrosine / Q000378:metabolism; D020298:U937 Cells
D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D014443:Tyrosine; D012694:Serine; D014212:Tretinoin