Components And Cofactors Of SWI/SNF Chromatin Remodeling Complex In Human Embryonic Stem Cells

The SWI/SNF complex is an evolutionally conserved and ATP-dependent multiple-subunit chromatin remodeling complex. Its core subunit Brgl or Brm has the ATPase activity, which use the energy of ATP hydrolysis to change the nucleosome structure, and thus to alter the accessibility of DNA for the transcriptionanl factors, and in turn to regulate gene expression. The SWI/SNF complex plays an important role in many cell biology processes, such as cell cycle, apoptosis and tumor formation. Recent studies demonstrated that specific components of SWI/SNF complex was essential for its function in mouse embryonic stem cells (ES). Using western blotting(WB), fast protein liquid chromatography (FPLC), coimmunoprecipitation (COIP), and mass spectrary analysis, we sought to reveal the specific components and cofactors of SWI/SNF complex in human ES. We observed that BRG、BAF155、 BAF170exist in same complex by FPLC. In addition, we found that BRG1interacted with BAF155and BAF170. The components of the SWI/SNF were different between HES、MES and HELA cells. In our functional study, knockdown of BRG1or BAF170but not BAF155results in differentiation of the HES,. These results suggested that the subunites existed in one complex,and they have different functions. To further explore the molecular mechanism of their different functions, we used CO-IP experiments coupled with mass spectrary analysis. The mass spectrary analysis indicated that the SWI/SNF complex contains at least17subunits and the ratio of each components was different from the mouse ES. In addition, we identified cofactors of the SWI/SNF complex participated in many cell biology processes, distinct from that was found in mouse ES. Furthermore, the cofactors of BRG1,BAF155and BAF170share similarities and differences,which may explain the function difference observed in different components in HES. In summary, SWI/SNF charomatin remodeling complex has an unique composition of components in HES, and its special function may be related to the cofactors.