Abstract: The objective of this work is to explore whether or not nucleoid-associated protein Lsr2 of Mycobacterium tuberculosis is a repressor protein in gene rv1057 expression. Electrophoretic mobility shift assay was used to analyze the in vivo specific binding capability of Lsr2 with the target gene promoter region.lacZ report gene and fluorescence quantitative PCR were adapted to detect the effects of different mutations of rv1057 promoter region on the transcription. Western blot was employed to analyze the protein expression level of target gene rv1057. The t test was used for statistical analysis. As results，Lsr2 was able to bind to rv1057 promoter. Both Lsr2 and the known repressor protein TrcR were able to bind to rv1057 promoter. The mutated rv1057 promoter lacking Lsr2 binding site was able to continuously activate the transcription of gene rv1057 during the growth cycle of M. tuberculosis. The relative expression of gene lsr2 was low in the early growth stage（24 h）of wild-type strain H37Rv，while the relative expression of gene lsr2 in H37Rv significantly increased both in the middle growth stage（48 h）and in the later growth stage（120 h），the difference was statistically significant（t=24.44，16.86，respectively；P<0.05）. The relative expression of the gene trcR of H37Rv and gene lsr2-deleted strain in the early growth stage（24 h）was significantly higher than in the middle growth period（48 h）and the later growth period（120 h），the difference was statistically significant（t=6.79，10.16，respectively；P<0.05）. In conclusion，Lsr2 is the repressor protein of gene rv1057 transcription. Both Lsr2 and TrcR may regulate the expression of rv1057. Lsr2 is mainly expressed in the middle and late growth period of the M. tuberculosis，and then represses the expression of rv1057；while TrcR represses the transcription of rv1057 in the early growth stage of the M. tuberculosis.

Key words: Mycobacterium tuberculosis, rv1057, Lsr2, repressor protein, regulating