Genome Sequence of the Siphoviridae Staphylococcus aureus Phage vB_SauS_BaqSau1

Here, we report the genome sequence of a Siphoviridae phage named vB_SauS_BaqSau1 (BaqSau1), infecting Staphylococcus aureus. Phage BaqSau1 was isolated from a sewage water treatment plant in Sahagún, Córdoba, Colombia. It has a double-stranded DNA (dsDNA) genome of 44,384 bp with 67 predicted genes, including a lysin containing a CHAP (cysteine, histidine-dependent amidohydrolase/ peptidase) domain

The Role of E6-Associated Protein in Estrogen Receptor Alpha Regulation

The Estrogen Receptor alpha (ER alpha) is a multi-domain transcription factor that has been extensively studied due to its known involvement in breast cancer treatment and progression. Subsequent studies have shown coregulators are extensively involved in modulating the transcriptional activation of ER alpha and many of these proteins possess enzymatic functions. Coregulators are divided into two categories, coactivators which enhance transcriptional output and corepressors which decrease transcriptional output. One protein responsible for Angelman syndrome, E6-associated protein (E6-AP) was found to be a coactivator of ER alpha and possessed ubiquitin ligase activity; however, the ubiquitin ligase activity has been shown not to be essential to E6-AP coactivation ability. The current work was undertaken to explore the role of E6-AP in the regulation of ER alpha. E6-AP was found to play a role in a unique ligand-independent degradation pathway. Because the degradation effect was ligand-independent, it was proposed that the degradation signal mediating the event occurred through phosphorylation of E6-AP. In silico analysis of E6-AP indicated several potential phosphorylation sites on the E6-AP protein. Numerous phosphorylation sites of E6-AP were confirmed by western blot and mass spec indicating a possible phosphorylation signal mediating E6-AP/ER alpha interaction. Because it has been shown that the ligase function of E6-AP is not required for its coactivation, we then examined E6-AP coactivation of ERα in the presence of ligand. One well studied gene TFF-1 (pS2) was examined as a model ERα target gene. Estrogen-mediated transcription from TFF-1 was decreased with knockdown of E6-AP in both MCF-7 and T47D cell lines. Furthermore, under E6-AP knockdown conditions, ChIP of p300, a known histone acetyl transferase (HAT), indicated a reduced recruitment to the TFF-1 promoter in both cell lines. Interestingly, the reduced recruitment of p300 had a cell specific effect on phosphorylated RNA polymerase II (pRNA pol II) recruitment indicating cell specific functions of E6-AP. Further investigation also found a gene specific effect for E6-AP on pRNA pol II recruitment. The current work provides a new role for E6-AP as a coactivator of ER alpha in the form of a scaffold allowing creation of fully functional transcription complexes in a gene and cell specific manner

E6-AP facilitates efficient transcription at estrogen responsive promoters through recruitment of chromatin modifiers

E6-AP is a known coactivator of the estrogen receptor alpha (ERα), however the coactivation mechanism of E6-AP is not clear. This work was undertaken to elucidate the coactivation mechanism of E6-AP. In order to examine the role of E6-AP in ERα signaling, we knocked-down the expression of E6-AP and examined the transactivation functions of ERα. Knockdown of E6-AP showed reduced mRNA production of the ERα target genes pS2 and GREB1 suggesting that E6-AP is required for their proper transcription facilitated by ERα. In order to study the mechanism(s) by which E6-AP regulates the transcriptional functions of ERα, we performed chromatin immunoprecipitation (ChIP) assays under E6-AP knockdown conditions. Our ChIP data suggest that knockdown of E6-AP leads to decreased recruitment of the histone acetylase p300 to the ERα target gene pS2 promoter as well as reduced histone modifications at the promoter. Although there was reduced p300 recruitment to the pS2 promoter, loss of p300 did not account fully for the loss of histone acetylation. Taken together our data suggest that E6-AP regulates the transactivation functions of ERα in part by complexing with p300 and other chromatin modifying enzymes at target gene promoters to create a transcriptionally active promoter environment