Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA.
Department of Molecular Genetics, The Forsyth Institute, Cambridge, MA, USA.
Microbiology (Reading). 2013 Feb;159(Pt 2):219-229. doi: 10.1099/mic.0.061002-0. Epub 2012 Nov 22.
HU is a non-sequence-specific DNA-binding protein and one of the most abundant nucleoid-associated proteins in the bacterial cell. Like Escherichia coli, the genome of Porphyromonas gingivalis is predicted to encode both the HUα (PG1258) and the HUβ (PG0121) subunit. We have previously reported that PG0121 encodes a non-specific DNA-binding protein and that PG0121 is co-transcribed with the K-antigen capsule synthesis operon. We also reported that deletion of PG0121 resulted in downregulation of capsule operon expression and produced a P. gingivalis strain that is phenotypically deficient in surface polysaccharide production. Here, we show through complementation experiments in an E. coli MG1655 hupAB double mutant strain that PG0121 encodes a functional HU homologue. Microarray and quantitative RT-PCR analysis were used to further investigate global transcriptional regulation by HUβ using comparative expression profiling of the PG0121 (HUβ) mutant strain to the parent strain, W83. Our analysis determined that expression of genes encoding proteins involved in a variety of biological functions, including iron acquisition, cell division and translation, as well as a number of predicted nucleoid associated proteins were altered in the PG0121 mutant. Phenotypic and quantitative real-time-PCR (qRT-PCR) analyses determined that under iron-limiting growth conditions, cell division and viability were defective in the PG0121 mutant. Collectively, our studies show that PG0121 does indeed encode a functional HU homologue, and HUβ has global regulatory functions in P. gingivalis; it affects not only production of capsular polysaccharides but also expression of genes involved in basic functions, such as cell wall synthesis, cell division and iron uptake.
HU 是一种非序列特异性的 DNA 结合蛋白，也是细菌细胞中最丰富的核基质相关蛋白之一。与大肠杆菌一样，牙龈卟啉单胞菌的基因组预计编码 HUα（PG1258）和 HUβ（PG0121）亚基。我们之前报道过 PG0121 编码一种非特异性 DNA 结合蛋白，并且 PG0121 与 K-抗原荚膜合成操纵子共转录。我们还报道过缺失 PG0121 会导致荚膜操纵子表达下调，并产生一种表型上缺乏表面多糖产生的牙龈卟啉单胞菌菌株。在这里，我们通过在大肠杆菌 MG1655 hupAB 双突变株中的互补实验表明，PG0121 编码一种功能性 HU 同源物。微阵列和定量 RT-PCR 分析用于通过比较 PG0121（HUβ）突变株与亲本菌株 W83 的表达谱进一步研究 HUβ 的全局转录调控。我们的分析确定，编码参与各种生物学功能的蛋白质的基因表达，包括铁摄取、细胞分裂和翻译，以及许多预测的核基质相关蛋白在 PG0121 突变株中发生改变。表型和定量实时-PCR（qRT-PCR）分析确定，在缺铁生长条件下，PG0121 突变体的细胞分裂和活力受损。总的来说，我们的研究表明 PG0121 确实编码一种功能性 HU 同源物，HUβ 在牙龈卟啉单胞菌中具有全局调节功能；它不仅影响荚膜多糖的产生，还影响细胞壁合成、细胞分裂和铁摄取等基本功能相关基因的表达。
