New Microtubule Binding Protein Nusap Mitotic Regulatory Function And Dna Binding Capacity

To reveal the mechanism of mitotic regulation is a key task of cell biological research. Mitotic spindle assembly and chromosome segregation, in which normal regulation of microtubules nucleation and dynamics is required, both play critical roles in mitosis. NuSAP (nucleolar spindle associated protein) is a novel microtubule associated protein with selective expression and localization during cell cycle progression. Its mRNA and protein levels peak at the transition of G2 to mitosis and decline after cell division. NuSAP is localized in the nucleus in interphase, and translocates to the spindle during mitosis phase. Overexpression of NuSAP or depletion of NuSAP by RNAi could result in spindle deficient. However, there are still several problems left. For example: What is the outcome, if NuSAP expresses in those cells in which endogenous NuSAP can not be detected. In addition, tissue distribution of NuSAP gene is still unkown.In this study, four conserved regions of NuSAP were discovered among different species, which correspond to the SAP domain, Nuclear localization signal and microtubule associated domain, indicating that conserved regions may play an important role in the function of NuSAP. NuSAP highly expressed in human fetal liver, thymus, bone and several leukemia cell lines, whereas low or undetectable in in three highly differentiated tissues( lymph node, spleen and Peripheral blood). It suggested NuSAP might play a role in premature hematopoietic and immune tissues.We further show that NuSAP could trigger M arrest in HEK293, COS7 and MCF7. Those cells with NuSAP expression were arrested in M phase at least 3 days and no attenuation was observed. Analysis of truncates of NuSAP, indicates MTs binding domain is necessary for triggering cell arrest.p53 and ATM are two key regulators of mitotic checkpoint. To reveal the...