PLU1 is a candidate oncogene that encodes H3K4 (Lys(4) of histone H3) demethylase. In the present study, we found that ectopic expression of PLU1 enhanced the invasive potential of the weakly invasive cells dependent on its demethylase activity. PLU1 was shown to repress the expression of the KAT5 gene through its H3K4 demethylation on the promoter. The regulation of KAT5 by PLU1 was suggested to be responsible for PLU1-induced cell invasion. First, knockdown of KAT5 similarly increased the invasive potential of the cells. Secondly, knockdown of PLU1 in the highly invasive cancer cells increased KAT5 expression and reduced the invasive activity. Thirdly, simultaneous knockdown of KAT5 partially relieved the suppression of cell invasion imposed by PLU1 knockdown. Finally, we found that CD82, which was transcriptionally regulated by KAT5, might be a candidate effector of cell invasion promoted by PLU1. The present study demonstrated a functional contribution of PLU1 overexpression with concomitant epigenetic dysregulation in cancer progression.
The switching of ADP-ribosylation factors from the inactive form to the active form is catalyzed by ARF-GEF (ADP ribosylation factor -guanine nucleotide exchange protein) proteins containing a Sec7 domain. The murine Arfgef2 gene encoding the BIG2 protein belongs to the class of high molecular mass (>100 kDa) ARF-GEF proteins. BIG2 is believed to be associated with the trans-Golgi network and the recycling endosomes. In humans, mutations in the ARFGEF2 gene cause autosomal recessive periventricular heterotopia with microcephaly. To elucidate the function of BIG2 in mouse we studied a gene-trap mouse line with a functional disruption of the Arfgef2 gene. Heterozygous mutants did not reveal phenotypic abnormalities and were fertile. However, no homozygous embryos were obtained from breeding heterozygous females and males. To explore the reason for embryonic lethality, we analysed the pattern of expression of Arfgef2. Arfgef2 transcripts were detected in several adult tissues. Interestingly, Arfgef2 undergoes alternative splicing and the splicing pattern differs among tissues from adult animals. Moreover, the LacZ reporter gene of the gene-trap construct was used to reveal the expression of Arfgef2 during embryonic development. Here, we show that Arfgef2 mRNA is stored in the oocyte and is likely translated during the first embryonic divisions. SNP (Single Nucleotide Polymorphism) markers were used to demonstrate that the embryonic Arfgef2 gene is activated first at the 4-cell stage, suggesting an important role for embryonic development. This assumption is supported by the failure of Arfgef2-deficient oocytes fertilized with Arfgef2-deficient sperm to develop into 4-cell stage embryos. Our results indicate that murine BIG2 is essential for early embryonic development.
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