ZBTB33 (Kaiso) Differentially Regulates Cell Cycle Through cyclin D1 and cyclin E1 in a Cell Specific Manner [RNA-seq]

The emerging correlation between aberrant DNA methylation patterns leading to transcriptional responses that promote and progress many cancers has prompted an interest in discerning the associated regulatory mechanisms. ZBTB33 (also known as Kaiso) is a specialized transcription factor that selectively recognizes mCpG-containing sites as well as a sequence-specific DNA target (termed the KBS) utilizing three Cys2His2 zinc fingers. Increasing reports link ZBTB33 overexpression and transcriptional activities with metastatic potential and poor prognosis, though the specific cellular consequences appear to be dependent on disease phenotype. There is currently little mechanistic insight into how various cellular phenotypes are then able to harness the transcriptional capabilities of ZBTB33 to differentially promote and progress the disease state. Here we have mechanistically interrogated the cell cycle responses mediated by the transcriptional activities of ZBTB33 in two different cell lines. Utilizing a series of ZBTB33 depletion and overexpression studies, we have determined that in HeLa cells ZBTB33 directly occupies the promoter regions of cyclin D1 and cyclin E1 in a KBS and methyl-specific manner, respectively, inducing increased proliferation by promoting RB1 hyper-phosphorylation, allowing for E2F transcriptional activity that coordinates an accelerated G1- to S-phase transition. Conversely, in HEK293 cells ZBTB33 indirectly regulates Cyclin E abundance resulting in reduced RB1 phosphorylation, decreased E2F activity and a decelerated transition through G1-phase. Thus, we have identified a novel mechanism by which ZBTB33 directly mediates the highly coordinated cyclin D1/cyclin E1/RB1/E2F signaling pathway controlling the passage through the G1-phase restriction point and accelerating cellular proliferation in a cancer cell line. Overall design: Determination of cellular and transcriptional consequences for ZBTB33 depletion in HeLa cells.

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Pozner A, Terooatea TW, Buck-Koehntop BA