Browsing by Author "Babu, M. Madan"

Now showing 1 - 5 of 5
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    Classification of Intrinsically Disordered Regions and Proteins
    (American Chemical Society, 2014-07-09) van der Lee, Robin; Buljan, Marija; Lang, Benjamin; Weatheritt, Robert J.; Daughdrill, Gary W.; Dunker, A. Keith; Fuxreiter, Monika; Gough, Julian; Gsponer, Joerg; Jones, David T.; Kim, Philip M.; Kriwacki, Richard W.; Oldfield, Christopher J.; Pappu, Rohit V.; Tompa, Peter; Uversky, Vladimir N.; Wright, Peter E.; Babu, M. Madan; Department of Biochemistry & Molecular Biology, IU School of Medicine
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    Dissecting the expression dynamics of RNA-binding proteins in posttranscriptional regulatory networks
    (2009-12) Mittal, Nitish; Roy, Nilanjan; Babu, M. Madan; Janga, Sarath Chandra
    In eukaryotic organisms, gene expression requires an additional level of coordination that links transcriptional and posttranslational processes. Messenger RNAs have traditionally been viewed as passive molecules in the pathway from transcription to translation. However, it is now clear that RNA-binding proteins (RBPs) play an important role in cellular homeostasis by controlling gene expression at the posttranscriptional level. Here, we show that RBPs, as a class of proteins, show distinct gene expression dynamics compared to other protein coding genes in the eukaryote Sacchoromyces cerevisiae. We find that RBPs generally exhibit high protein stability, translational efficiency, and protein abundance but their encoding transcripts tend to have a low half-life. We show that RBPs are also most often posttranslationally modified, indicating their potential for regulation at the protein level to control diverse cellular processes. Further analysis of the RBP-RNA interaction network showed that the number of distinct targets bound by an RBP (connectivity) is strongly correlated with its protein stability, translational efficiency, and abundance. We also note that RBPs show less noise in their expression in a population of cells, with highly connected RBPs showing significantly lower noise. Our results indicate that highly connected RBPs are likely to be tightly regulated at the protein level as significant changes in their expression may bring about large-scale changes in global expression levels by affecting their targets. These observations might explain the molecular basis behind the cause of a number of disorders associated with misexpression or mutation in RBPs. Future studies uncovering the posttranscriptional networks in higher eukaryotes can help our understanding of the link between different levels of regulation and their role in pathological conditions.
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    DNA Sequence Preferences of Transcriptional Activators Correlate More Strongly than Repressors with Nucleosomes
    (2012-07) Charoensawan, Varodom; Janga, Sarath Chandra; Bulyk, Martha L.; Babu, M. Madan; Teichmann, Sarah A.
    Transcription factors (TFs) and histone octamers are two abundant classes of DNA binding proteins that coordinate the transcriptional program in cells. Detailed studies of individual TFs have shown that TFs bind to nucleosome-occluded DNA sequences and induce nucleosome disruption/repositioning, while recent global studies suggest this is not the only mechanism used by all TFs. We have analyzed to what extent the intrinsic DNA binding preferences of TFs and histones play a role in determining nucleosome occupancy, in addition to nonintrinsic factors such as the enzymatic activity of chromatin remodelers. The majority of TFs in budding yeast have an intrinsic sequence preference overlapping with nucleosomal histones. TFs with intrinsic DNA binding properties highly correlated with those of histones tend to be associated with gene activation and might compete with histones to bind to genomic DNA. Consistent with this, we show that activators induce more nucleosome disruption upon transcriptional activation than repressors.
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    Network-based approaches for linking metabolism with environment
    (2008-11) Janga, Sarath Chandra; Babu, M. Madan
    Progress in the reconstruction of genome-wide metabolic maps has led to the development of network-based computational approaches for linking an organism with its biochemical habitat.
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    Transcriptional regulation constrains the organization of genes on eukaryotic chromosomes
    (2008-10) Janga, Sarath Chandra; Collado-Vides, Julio; Babu, M. Madan
    Genetic material in eukaryotes is tightly packaged in a hierarchical manner into multiple linear chromosomes within the nucleus. Although it is known that eukaryotic transcriptional regulation is complex and requires an intricate coordination of several molecular events both in space and time, whether the complexity of this process constrains genome organization is still unknown. Here, we present evidence for the existence of a higher-order organization of genes across and within chromosomes that is constrained by transcriptional regulation. In particular, we reveal that the target genes (TGs) of transcription factors (TFs) for the yeast, Saccharomyces cerevisiae, are encoded in a highly ordered manner both across and within the 16 chromosomes. We show that (i) the TGs of a majority of TFs show a strong preference to be encoded on specific chromosomes, (ii) the TGs of a significant number of TFs display a strong preference (or avoidance) to be encoded in regions containing particular chromosomal landmarks such as telomeres and centromeres, and (iii) the TGs of most TFs are positionally clustered within a chromosome. Our results demonstrate that specific organization of genes that allowed for efficient control of transcription within the nuclear space has been selected during evolution. We anticipate that uncovering such higher-order organization of genes in other eukaryotes will provide insights into nuclear architecture, and will have implications in genetic engineering experiments, gene therapy, and understanding disease conditions that involve chromosomal aberrations.