GJA1 reverses arsenic-induced EMT via modulating MAPK/ERK signaling pathway.

Arsenic is known as a well-established human carcinogen. Gap Junction Protein Alpha 1 (GJA1) is a multifunction protein that forms gap junction channels and is important for intercellular communication. Recently, its aberrant expression has been shown to associate with cancer recurrence and metastatic spread. However, whether GJA1 plays a role in arsenic carcinogenesis remains unknown. Here, we demonstrated that chronic exposure of human bronchial epithelial BEAS-2B cells to sodium arsenite promoted epithelial-mesenchymal transition (EMT) via increasing the expression of EMT inducer S100A4 and activation of MAPK/ERK signaling. In vitro and in vivo experiments showed that chronic exposure to sodium arsenite reduced GJA1 expression. Forced expression of GJA1 inhibited sodium arsenite-induced EMT via suppressing MAPK/ERK signaling whereas GJA1 knockdown produced an opposite effect. Intriguingly, chronic exposure to sodium arsenite increased autophagy flux. Inhibition of autophagy by pharmacological intervention or genetic deletion of autophagy core gene Beclin-1 upregulated GJA1 expression. These results suggested that GJA1 restrained the carcinogenic effect of sodium arsenite by limiting MAPK/ERK signaling, and GJA1 expression was decreased by arsenic-activated autophagy. In addition, interventions directed at enhancing the level or functional activity of GJA1 could be of preventive and therapeutic interest.

Production of marker-free and RSV-resistant transgenic rice using a twin T-DNA system and RNAi.

A twin T-DNA system is a convenient strategy for creating selectable marker-free transgenic plants. The standard transformation plasmid, pCAMBIA 1300, was modified into a binary vector consisting of two separate T-DNAs, one of which contained the hygromycin phosphotransferase (hpt) marker gene. Using this binary vector, we constructed two vectors that expressed inverted-repeat (IR) structures targeting the rice stripe virus (RSV) coat protein (CP) gene and the special-disease protein (SP) gene. Transgenic rice lines were obtained via Agrobacterium-mediated transformation. Seven independent clones harbouring both the hpt marker gene and the target genes (RSV CP or SP) were obtained in the primary transformants of pDTRSVCP and pDTRSVSP, respectively. The segregation frequencies of the target gene and the marker gene in the T1 plants were 8.72 percent for pDTRSVCP and 12.33 percent for pDTRSVSP. Two of the pDTRSVCP lines and three pDTRSVSP lines harbouring the homozygous target gene, but not the hpt gene, were strongly resistant to RSV. A molecular analysis of the resistant transgenic plants confirmed the stable integration and expression of the target genes. The resistant transgenic plants displayed lower levels of the transgene transcripts and specific small interfering RNAs, suggesting that RNAi induced the viral resistance.