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Φm46.1, the Main Streptococcus pyogenes Element Carrying mef(A) and tet(O) Genes▿

Brenciani, Andrea; Bacciaglia, Alessandro; Vignaroli, Carla; Pugnaloni, Armanda; Varaldo, Pietro E.; Giovanetti, Eleonora
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Φm46.1, the recognized representative of the most common variant of mobile, prophage-associated genetic elements carrying resistance genes mef(A) (which confers efflux-mediated erythromycin resistance) and tet(O) (which confers tetracycline resistance) in Streptococcus pyogenes, was fully characterized. Sequencing of the Φm46.1 genome (55,172 bp) demonstrated a modular organization typical of tailed bacteriophages. Electron microscopic analysis of mitomycin-induced Φm46.1 revealed phage particles with the distinctive icosahedral head and tail morphology of the Siphoviridae family. The chromosome integration site was within a 23S rRNA uracil methyltransferase gene. BLASTP analysis revealed that the proteins of Φm46.1 had high levels of amino acid sequence similarity to the amino acid sequences of proteins from other prophages, especially Φ10394.4 of S. pyogenes and λSa04 of S. agalactiae. Phage DNA was present in the host cell both as a prophage and as free circular DNA. The lysogeny module appears to have been split due to the insertion of a segment containing tet(O) (from integrated conjugative element 2096-RD.2) and mef(A) (from a Tn1207.1-like transposon) into the unintegrated phage DNA. The phage attachment sequence lies in the region between tet(O) and mef(A) in the unintegrated form. Thus...

ELF4/MEF Activates MDM2 Expression and Blocks Oncogene-Induced p16 Activation To Promote Transformation▿ †

Sashida, Goro; Liu, Yan; Elf, Shannon; Miyata, Yasuhiko; Ohyashiki, Kazuma; Izumi, Miki; Menendez, Silvia; Nimer, Stephen D.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Several ETS transcription factors, including ELF4/MEF, can function as oncogenes in murine cancer models and are overexpressed in human cancer. We found that Elf4/Mef activates Mdm2 expression; thus, lack of or knockdown of Elf4/Mef reduces Mdm2 levels in mouse embryonic fibroblasts (mef's), leading to enhanced p53 protein accumulation and p53-dependent senescence. Even though p53 is absent in Elf4−/− p53−/− mef's, neither oncogenic H-RasV12 nor c-myc can induce transformation of these cells. This appears to relate to the INK4a/ARF locus; both p19ARF and p16 are increased in Elf4−/− p53−/− mef's, and expression of Bmi-1 or knockdown of p16 in this context restores H-RasV12-induced transformation. Thus, ELF4/MEF promotes tumorigenesis by inhibiting both the p53 and p16/Rb pathways.