Dataset Information

Functional analysis of an intergenic non-coding sequence within mce1 operon of M.tuberculosis.

ABSTRACT:

Background

The mce operons play an important role in the entry of M. tuberculosis into macrophages and non-phagocytic cells. Their non-redundant function as well as complex regulation is implied by the phenotype of mce mutants. Recently, mce1 operon was found to extend over 13 genes, fadD5 (Rv0166) being the first gene of the operon. The presence of a non-coding sequence of 200 base pairs between Rv0166 and Rv0167 is peculiar to mce1 among the four mce operons of M.tuberculosis. We have examined the function of this region.

Results

We predicted putative promoter activity of the 200 base pairs of non-coding, intergenic region between Rv0166 and Rv0167 in silico using MEME software and designate it as intergenic promoter, IGPr. We demonstrate both promoter activity and a putative negative regulatory function of this fragment by reporter assays carried out in the surrogate host M.smegmatis. We find that the repressive elements not only control the native promoter but also repress a heterologous promoter of M.smegmatis. The higher activity of the intergenic promoter in a clinical isolate in comparison with the wild type sequence from M.tuberculosis H37Rv could be correlated with a point mutation within the negative element. We have mapped two transcription start sites for mce1 operon both of which are utilized in M.tuberculosis H37Rv as well as the clinical isolate VPCI591. Our studies show that the promoter activity in the non-coding region is relevant not only in reporter gene expression but also in the expression of mce1 operon in M. tuberculosis cells grown in synthetic medium.

Conclusion

The mce operon of M.tuberculosis H37Rv potentially can be transcribed from two promoters P1 and P2, former mapping upstream of Rv0166 and the latter in the non-coding intergenic region between Rv0166 and Rv0167. The transcription initiation from P1 results in a transcript with Rv0166 while that from P2 will be without it. The sequences between the translation start site of Rv0167 and the promoter P2 have a negative regulatory role, as point mutation within the sequence leads to enhanced activity of P2 as well as a heterologous promoter from M.smegmatis. The mutation detected in the clinical isolate VPCI591 therefore behaves like a gain-of-function mutation.

SUBMITTER: Joon M

PROVIDER: S-EPMC2867952 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Recently, large numbers of normal human tissues have been profiled for non-coding RNAs and more than fourteen thousand long intergenic non-coding RNAs (lincRNAs) are found expressed in normal human tissues. The functional roles of these normal lincRNAs (nlincRNAs) in the regulation of protein coding genes in normal and disease biology are yet to be established. Here, we have profiled two RNA-seq datasets including cancer and matched non-neoplastic tissues from 12 individuals from diverse demography for both coding genes and nlincRNAs. We find 130 nlincRNAs significantly regulated in cancer, with 127 regulated in the same direction in the two datasets. Interestingly, according to Illumina Body Map, significant numbers of these nlincRNAs display baseline null expression in normal prostate tissues but are specific to other tissues such as thyroid, kidney, liver and testis. A number of the regulated nlincRNAs share loci with coding genes, which are either co-regulated or oppositely regulated in all cancer samples studied here. For example, in all cancer samples i) the nlincRNA, TCONS_00029157, and a neighboring tumor suppressor factor, SIK1, are both down regulated; ii) several thyroid-specific nlincRNAs in the neighborhood of the thyroid-specific gene TPO, are both up-regulated; and iii) the TCONS_00010581, an isoform of HEIH, is down-regulated while the neighboring EZH2 gene is up-regulated in cancer. Several nlincRNAs from a prostate cancer associated chromosomal locus, 8q24, are up-regulated in cancer along with other known prostate cancer associated genes including PCAT-1, PVT1, and PCAT-92. We observe that there is significant bias towards up-regulation of nlincRNAs with as high as 118 out of 127 up-regulated in cancer, even though regulation of coding genes is skewed towards down-regulation. Considering that all reported cancer associated lincRNAs (clincRNAs) are biased towards up-regulation, we conclude that this bias may be functionally relevant.