Human PUF-A/PUM3 is a RNA and DNA binding protein participating in the nucleolar processing of 7S to 5.8S rRNA. The nucleolar localization of PUF-A redistributes to the nucleoplasm upon the exposure to genotoxic agents in cells. However, little is known regarding the roles of PUF-A in tumor progression. Phosphoprotein database analysis revealed that Y259 phosphorylation of PUF-A is the most prevalent residue modified. Here, we reported the importance of PUF-A's phosphorylation on Y259 in tumorigenesis. PUF-A gene was knocked out by the Crispr/Cas9 method in human cervix epithelial HeLa cells. Loss of PUF-A in HeLa cells resulted in reduced clonogenic and lower transwell invasion capacity. Introduction of PUF-AY259F to PUF-A deficient HeLa cells was unable to restore colony formation. In addition, the unphosphorylated mutant of PUF-A, PUF-AY259F, attenuated PUF-A protein stability. Our results suggest the important role of Y259 phosphorylation of PUF-A in cell proliferation.