Functional proteomic studies to identify Oct4A possible interactors.

Abstract

Oct‐4A (Octamer binding protein 4, isoform A) is a key component of the molecular circuitry which regulates stem cells self‐renewal and pluripotency. Very little is known about the mechanisms through which Oct‐4A responds to complex extracellular stimuli and regulates stemness. In our studies we noted that Oct‐4 was expressed both in nucleus and cytoplasm, implicating the presence of nuclear‐cytoplamatic translocation mechanisms. To further explore the functional network of Oct‐4A, in vitro and in vivo methods were used to search interacting proteins in human Dental Pulp Marrow Similar Cells (DPMSC) and NTera2, a human embryonal carcinoma (EC) stem cell line that shares many characteristics with human embryonic stem cells. Glutathione S‐transferase pull‐down and co‐immunoprecipitation assays identified Erk1/2 as a possible Oct‐4A interactor. One mechanism by which Erk1/2 kinases ensure their specificity of action is by interacting with their substrates through docking domains, enhancing also the efficiency of phosphorylation. Oct‐4A sequence analysis evidenced the presence of a D‐domain supporting our interaction hypothesis. Further studies are needed to better understand the mechanism.