| Popis: |
Typically, levels of inhibitor of DNA binding 1 (IdI) are high in stem cells and decrease upon senescence or differentiation. Defining how IdI expression is regulated is critical to understanding what happens at the molecular level as cells differentiate during development and age in the adult organism. It has been proposed that zinc finger E-box binding protein (Zeb)l is a repressor of the pluripotency regulator Nanog and that IdI maintains embryonic stem (ES) cell pluripotency by inhibiting Zebl expression. However, ablation of Id1 in mouse ES cells did not alter Zebl protein levels. Somatic cells can be reprogrammed to pluripotency. The initiation of reprogramming without feeder cells was impaired in Id1 -/- and Id3 -/- MEFs. However, no difference was observed between WT and Id1 -/- in the presence of feeder cells. As MEFs were maintained in vitro and approached senescence, Idl protein, but not transcript, decreased. microRNAs are short, non-coding RNAs that inhibit mRNA expression by binding to the 3' untranslated region (UTR), resulting in either degradation or translational repression of the transcript. The 3' UTRs of mouse Idl - Id4 were cloned into a reporter vector. Reporter transcripts were repressed by the Idl 3' UTR, unlike other family members. A 67 base region of the IdI 3' UTR that was necessary for repression contained a predicted miR-381 / miR-539-3p binding site. A single point mutation at this site relieved repression by the Idl 3' UTR in a reporter vector. However, attempts to modulate activity of these microRNAs did not alter repression by the IdI 3' UTR in a reporter vector, or Id l protein levels. The present work has identified a previously unknown regulatory element located in a highly conserved region of the 3' UTR of Idl. Whereas the mechanism of regulation is unclear, tools have been generated that will allow manipulation of this site in a variety of cell lines. |
