CP2b synergies the transcriptional activity of CP2c by heteromerization with the DNA bound CP2c in a cell context-dependent manner

초록

As a member of ubiquitous transcription factor family, how CP2 critically exerts its effect on the expression of a variety of tissue-specific genes? As an effort to address this question, we previously identified three mouse CP2 family genes, CP2a, CP2b, and CP2c, and demonstrated that they are distinguished in their intrinsic DNA binding and transcription activities. Here, as a better understanding on tissue-specific expression of the CP2 target genes, we tested how CP2b affects the CP2c activity on the ?-globin promoter by transfection assays of a reporter construct in two different cell lines, kidney 293T cells and erythroleukemic K562 cells in which endogenous globin genes are expressing. Whereas both transcriptional and DNA binding abilities of CP2c were suppressed by CP2b in 293T cells, CP2c activity was rather augmented by CP2b in K562 cells. Moreover, this CP2b effect on CP2c in K562 cells was reduced by either co-expression of the CP2c dominant-negative or the N-terminal deletion-mutant of CP2b. We confirmed by electrophoretic mobility shift assays that CP2b exerts its effect by heteromerization with the DNA-bound CP2c in K562 cells. Overall data suggests that CP2b activity is regulated by a novel CP2b modification and/or interaction with other partner proteins in a cell context-dependent manner and, consequently, the activated CP2b synergizes the transcriptional activity of CP2c by heteromerization with the DNA-bound CP2c.