• Sanjeev Galande

      Articles written in Journal of Biosciences

    • N-terminal PDZ-like domain of chromatin organizer SATB1 contributes towards its function as transcription regulator

      Dimple Notani Praveena L Ramanujam P Pavan Kumar Kamalvishnu P Gottimukkala Chandan Kumar-Sinha Sanjeev Galande

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      The special AT-rich DNA-binding protein 1 (SATB1) is a matrix attachment region (MAR)-binding protein that acts as a global repressor via recruitment of CtBP1:HDAC1-containing co-repressors to its binding targets. The N-terminal PSD95/Dlg-A/ZO-1 (PDZ)-like domain of SATB1 mediates interactions with several chromatin proteins. In the present study, we set out to address whether the PDZ-domain-mediated interactions of SATB1 are critical for its in vivo function as a global repressor. We reasoned that since the N-terminal PDZ-like domain (amino acid residues 1–204) lacks DNA binding activity, it would fail to recruit the interacting partners of SATB1 to its genomic binding sites and hence would not repress the SATB1-regulated genes. Indeed, in vivo MAR-linked luciferase reporter assay revealed that overexpression of the PDZ-like domain resulted in de-repression, indicating that the PDZ-like domain exerts a dominant negative effect on genes regulated by SATB1. Next, we developed a stable dominant negative model in human embryonic kidney (HEK) 293T cells that conditionally expressed the N-terminal 1–204 region harbouring the PDZ-like domain of SATB1. To monitor the effect of sequestration of the interaction partners on the global gene regulation by SATB1, transcripts from the induced and uninduced clones were subjected to gene expression profiling. Clustering of expression data revealed that 600 out of 19000 genes analysed were significantly upregulated upon overexpression of the PDZ-like domain. Induced genes were found to be involved in important signalling cascades and cellular functions. These studies clearly demonstrated the role of PDZ domain of SATB1 in global gene regulation presumably through its interaction with other cellular proteins.

    • Comparative sequence analyses of genome and transcriptome reveal novel transcripts and variants in the Asian elephant Elephas maximus

      Puli Chandramouli Reddy Ishani Sinha Ashwin Kelkar Farhat Habib Saurabh J Pradhan Raman Sukumar Sanjeev Galande

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      The Asian elephant Elephas maximus and the African elephant Loxodonta africana that diverged 5-7 million years ago exhibit differences in their physiology, behaviour and morphology. A comparative genomics approach would be useful and necessary for evolutionary and functional genetic studies of elephants. We performed sequencing of E. maximus and map to L. africana at ∼ 15X coverage. Through comparative sequence analyses, we have identified Asian elephant specific homozygous, non-synonymous single nucleotide variants (SNVs) that map to 1514 protein coding genes, many of which are involved in olfaction. We also present the first report of a high-coverage transcriptome sequence in E. maximus from peripheral blood lymphocytes. We have identified 103 novel protein coding transcripts and 66-long non-coding (Inc)RNAs. We also report the presence of 181 protein domains unique to elephants when compared to other Afrotheria species. Each of these findings can be further investigated to gain a better understanding of functional differences unique to elephant species, as well as those unique to elephantids in comparison with other mammals. This work therefore provides a valuable resource to explore the immense research potential of comparative analyses of transcriptome and genome sequences in the Asian elephant.

    • Structure function relations in PDZ-domain-containing proteins: Implications for protein networks in cellular signalling

      G P MANJUNATH PRAVEENA L RAMANUJAM SANJEEV GALANDE

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      Protein scaffolds as essential backbones for organization of supramolecular signalling complexes are a recurrent theme inseveral model systems. Scaffold proteins preferentially employ linear peptide binding motifs for recruiting their interactionpartners. PDZ domains are one of the more commonly encountered peptide binding domains in several proteins includingthose involved in scaffolding functions. This domain is known for its promiscuity both in terms of ligand selection, mode ofinteraction with its ligands as well as its association with other protein interaction domains. PDZ domains are subject toseveral means of regulations by virtue of their functional diversity. Additionally, the PDZ domains are refractive to theeffect of mutations and maintain their three-dimensional architecture under extreme mutational load. The biochemical andbiophysical basis for this selectivity as well as promiscuity has been investigated and reviewed extensively. The presentreview focuses on the plasticity inherent in PDZ domains and its implications for modular organization as well as evolutionof cellular signalling pathways in higher eukaryotes.

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