OLA1 Maintains Cell Proliferation And Mouse Embryo Development By Repressing P53 And P21

Background:Obg-like ATPase 1(OLA1, also known as DOC45) belongs to the translation-factor-related (TRAFAC) class, Obg family, and YchF subfamily of P-loop GTPases. The TRAFAC GTPases include not only translation factors and ribosome-associated proteins, but proteins involved in signal transduction, intracellular transport, and stress response. However, it is unclear whether the YchF/OLA1 proteins are essential for life. At present, there still lack of a more robust model, such as null mutation, for future investigation. Besides, it is also necessary to characterize functions of OLA1 in the context of a living animal.Methods and contents:Generation of mouse strains carrying Ola1 null mutations, all Ola1-/- embryos and mice are the experiment group, while Ola1+/+ embryos are the control group, we observe and analyze their characteristics of growth and development;Generation of primary mouse fibroblasts(MEFs) which are isolated from E12.5 or E14.5 Ola1-/- embryos and Ola1+/+ embryos, do research on the molecular mechanisms of the stunted growth retardation in Ola1-/- group.Hence we have found the upregulation of cell cycle checkpoint p53/p21 in Ola1-/-group, we try to find how OLA1 regulate the expression of p53 and p21.Results:We present here the first analysis of Ola1 null mice. We show that disruption of Ola1 in mice causes a severer but incomplete perinatal lethality. All Ola1-/- embryos showed stunted growth coupled with delayed development, and as a result, organ immaturity at birth, especially in the lungs. The Ola1-/- primary mouse embryonic fibroblasts (MEF) exhibited markedly decreased cell proliferation owing to delayed G1-to-S phase transition, without changes in apoptosis. This cell cycle blockage was associated with reduced induction of cyclins D1 and E1, and attenuated Rb phosphorylation, but sustained high levels of p53 and p21Cipl/Wafl.By analyzing gene transcription, polysome profiling, and protein degradation, we revealed that the accumulation of p53 and p21 in Ola1-/- MEF was caused by increased stability and enhanced translation, respectively. Moreover, increased p21,independent of p53,was evidenced in Ola1-/- embryos with reduced cell proliferation.Conclusion:Together, these data demonstrate for the first time that OLA1, a translational GTPase, regulates p53 and p21 through a unique translational/post-translational mechanism, accumulation of p53 in Ola1-/- cells was attributable to increased protein stability, and that of p21 was caused by increased translation on p21 mRNA with a 5’UTR variant that lacks upstream open reading frame (uORF), which is required in mammals for maintaining adequate cell proliferation for successful development. These findings suggest that OLA1 is a novel regulator of the p53/p21 axis of the Gl/S checkpoint pathway, and plays a pivotal role in cell proliferation, mammalian development, and the growth of the whole organism.