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首页> 外文期刊>Infection and immunity >DNA sequencing and gene expression of the emm gene cluster in an M50 group A streptococcus strain virulent for mice.
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DNA sequencing and gene expression of the emm gene cluster in an M50 group A streptococcus strain virulent for mice.

机译：M50 A组链球菌对小鼠有毒力的emm基因簇的DNA测序和基因表达。

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The strain B514, an M serotype 50 strain, is capable of causing a natural upper respiratory infection leading to death in mice, as reported by Hook et al. in 1960 (E. W. Hook, R. R. Wagner, and R. C. Lancefield, Am. J. Hyg. 72:111-119, 1960). Thus, this strain was of interest for use in developing an animal model for group A streptococcal colonization and disease. The emm gene cluster for this strain was examined by PCR mapping and found to contain three emm family genes and cluster pattern 5. PCR-generated fragments corresponding to the SF4 (mrp50), SF2 (emmL50), and SF3 (enn50) genes were cloned and the entire gene cluster was sequenced. The gene cluster has greater than 97% DNA identity to previously sequenced regions of the gene cluster of the M2 strain T2/44/RB4 if two small divergent regions that encode the mature amino terminus of the SF-2 and SF-3 gene products are not included. If expressed, the genes encode proteins which bind human immunoglobulin G (Mrp50 and EmmL50) or immunoglobulin A (Enn50). However, in isolates taken directly after passage in mice, the surface proteins arising from these genes were barely detectable. The transcription of each gene in the B514 strain was investigated by Northern (RNA) hybridization, and mRNA transcripts were detected and quantitated relative to those of the recA gene, a housekeeping gene. Transcription of all three emm family genes was found to be over 30-fold attenuated relative to transcription of the same genes in strain T2/44/RB4. This suggests that the positive regulator, Mga, either is not expressed in this strain or has a different requirement for activation; it also suggests that the capsule may be sufficient to inhibit phagocytosis under these circumstances.
机译：如Hook等报道，菌株B514是M血清型50株，能够引起自然上呼吸道感染，导致小鼠死亡。 1960年（E. W. Hook，R。R. Wagner和R. C. Lancefield，美国Am。J. Hyg。72：111-119，1960年）。因此，该菌株可用于开发A组链球菌定植和疾病的动物模型。通过PCR定位检查了该菌株的emm基因簇，发现它包含三个emm家族基因和簇模式5。克隆了PCR生成的对应于SF4（mrp50），SF2（emmL50）和SF3（enn50）基因的片段然后对整个基因簇进行测序。如果两个编码SF-2和SF-3基因产物成熟氨基末端的小差异区域是M2株T2 / 44 / RB4的基因簇的先前测序区域，则该基因簇具有大于97％的DNA同一性。不包含。如果表达，则基因编码结合人免疫球蛋白G（Mrp50和EmmL50）或免疫球蛋白A（Enn50）的蛋白质。但是，在传给小鼠后直接分离的分离物中，几乎检测不到这些基因产生的表面蛋白。通过Northern（RNA）杂交研究了B514菌株中每个基因的转录，并且相对于管家基因recA基因的mRNA转录本进行了检测和定量。发现相对于菌株T2 / 44 / RB4中相同基因的转录，所有三个emm家族基因的转录衰减都超过30倍。这表明在该菌株中不表达正调节剂Mga，或者对激活有不同的要求。这也表明在这种情况下，该胶囊可能足以抑制吞噬作用。

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