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Singh, Umashankar
Publications (6 of 6) Show all publications
Agarwal, P., Enroth, S., Teichmann, M., Jernberg Wiklund, H., Smit, A., Westermark, B. & Singh, U. (2016). Growth signals employ CGGBP1 to suppress transcription of Alu-SINEs. Cell Cycle, 15(12), 1558-1571
Open this publication in new window or tab >>Growth signals employ CGGBP1 to suppress transcription of Alu-SINEs
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2016 (English)In: Cell Cycle, ISSN 1538-4101, E-ISSN 1551-4005, Vol. 15, no 12, p. 1558-1571Article in journal (Refereed) Published
Abstract [en]

CGGBP1 (CGG triplet repeat-binding protein 1) regulates cell proliferation, stress response,cytokinesis, telomeric integrity and transcription. It could affect these processes by modulatingtarget gene expression under different conditions. Identification of CGGBP1-target genes andtheir regulation could reveal how a transcription regulator affects such diverse cellular processes.Here we describe the mechanisms of differential gene expression regulation by CGGBP1 inquiescent or growing cells. By studying global gene expression patterns and genome-wide DNAbindingpatterns of CGGBP1, we show that a possible mechanism through which it affects theexpression of RNA Pol II-transcribed genes in trans depends on Alu RNA. We also show that itregulates Alu transcription in cis by binding to Alu promoter. Our results also indicate thatpotential phosphorylation of CGGBP1 upon growth stimulation facilitates its nuclear retention,Alu-binding and dislodging of RNA Pol III therefrom. These findings provide insights into howAlu transcription is regulated in response to growth signals.

Keywords
Alu-SINEs; CGGBP1; ChIP-seq; growth signals; RNA Pol III; transcription; tyrosine phosphorylation
National Category
Cell Biology
Research subject
Bioinformatics; Biology
Identifiers
urn:nbn:se:uu:diva-230959 (URN)10.4161/15384101.2014.967094 (DOI)000379743800011 ()25483050 (PubMedID)
Funder
Swedish Cancer SocietySwedish Research Council
Available from: 2014-09-01 Created: 2014-09-01 Last updated: 2017-12-05Bibliographically approved
Agarwal, P., Collier, P., Fritz, M.-Y. H., Benes, V., Wiklund, H. J., Westermark, B. & Singh, U. (2015). CGGBP1 mitigates cytosine methylation at repetitive DNA sequences. BMC Genomics, 16, Article ID 390.
Open this publication in new window or tab >>CGGBP1 mitigates cytosine methylation at repetitive DNA sequences
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2015 (English)In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 16, article id 390Article in journal (Refereed) Published
Abstract [en]

Background: CGGBP1 is a repetitive DNA-binding transcription regulator with target sites at CpG-rich sequences such as CGG repeats and Alu-SINEs and L1-LINEs. The role of CGGBP1 as a possible mediator of CpG methylation however remains unknown. At CpG-rich sequences cytosine methylation is a major mechanism of transcriptional repression. Concordantly, gene-rich regions typically carry lower levels of CpG methylation than the repetitive elements. It is well known that at interspersed repeats Alu-SINEs and L1-LINEs high levels of CpG methylation constitute a transcriptional silencing and retrotransposon inactivating mechanism. Results: Here, we have studied genome-wide CpG methylation with or without CGGBP1-depletion. By high throughput sequencing of bisulfite-treated genomic DNA we have identified CGGBP1 to be a negative regulator of CpG methylation at repetitive DNA sequences. In addition, we have studied CpG methylation alterations on Alu and L1 retrotransposons in CGGBP1-depleted cells using a novel bisulfite-treatment and high throughput sequencing approach. Conclusions: The results clearly show that CGGBP1 is a possible bidirectional regulator of CpG methylation at Alus, and acts as a repressor of methylation at L1 retrotransposons.

National Category
Medical Genetics
Identifiers
urn:nbn:se:uu:diva-256126 (URN)10.1186/s12864-015-1593-2 (DOI)000354528700001 ()25981527 (PubMedID)
Available from: 2015-06-22 Created: 2015-06-22 Last updated: 2018-01-11Bibliographically approved
Singh, U., Maturi, V., Jones, R. E., Paulsson, Y., Baird, D. M. & Westermark, B. (2014). CGGBP1 phosphorylation constitutes a telomere-protection signal. Cell Cycle, 13(1), 96-105
Open this publication in new window or tab >>CGGBP1 phosphorylation constitutes a telomere-protection signal
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2014 (English)In: Cell Cycle, ISSN 1538-4101, E-ISSN 1551-4005, Vol. 13, no 1, p. 96-105Article in journal (Refereed) Published
Abstract [en]

The shelterin proteins are required for telomere integrity. Shelterin dysfunction can lead to initiation of unwarranted DNA damage and repair pathways at chromosomal termini. Interestingly, many shelterin accessory proteins are involved in DNA damage signaling and repair. We demonstrate here that in normal human fibroblasts, telomeric ends are protected by phosphorylation of CGG triplet repeat-binding protein 1 (CGGBP1) at serine 164 (S164). We show that serine 164 is a major phosphorylation site on CGGBP1 with important functions. We provide evidence that one of the kinases that can phosphorylate S164 CGGBP1 is ATR. Overexpression of S164A phospho-deficient CGGBP1 exerted a dominant-negative effect, causing telomeric dysfunction, accelerated telomere shortening, enhanced fusion of telomeres, and crisis. However, overexpression of wild-type or phospho-mimicking S164E CGGBP1 did not cause these effects. This telomere damage was associated with reduced binding of the shelterin protein POT1 to telomeric DNA. Our results suggest that CGGBP1 phosphorylation at S164 is a novel telomere protection signal, which can affect telomere-protective function of the shelterin complex.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-221535 (URN)10.4161/cc.26813 (DOI)000331449600019 ()24196442 (PubMedID)
Available from: 2014-04-01 Created: 2014-04-01 Last updated: 2017-12-05Bibliographically approved
Singh, U., Maturi, V. & Westermark, B. (2013). Evidence for multiple forms and modifications of human POT1 [Letter to the editor]. DNA Repair, 12(11), 876-877
Open this publication in new window or tab >>Evidence for multiple forms and modifications of human POT1
2013 (English)In: DNA Repair, ISSN 1568-7864, E-ISSN 1568-7856, Vol. 12, no 11, p. 876-877Article in journal, Letter (Refereed) Published
Abstract [en]

Human POT1, a widely studied telomere protector protein is perceived to be expressed as a single 70 kDa form. A survey of the literature as well as different commercially available antibodies against POT1 suggests occurrence of multiple forms of POT1. Knowledge about possible various forms of an important protein like POT1 is necessary for our understanding about its function. We have discovered that POT1 exists in at least three consistently occurring forms; 90,70 and 45 kDa. The unexpected molecular weights of POT1 seem to be associated with SUMO1 and ubiquitin conjugation; the latter occurring at a double lysine residue at 289-KK-290. We also present evidence that the relative abundance of the different POT1 forms can be altered by experimental modulation of POT1 nuclear localization. We thus present strong evidence that there are post-translational modifications of POT1 that can affect its molecular weight as well as intracellular localization and function.

Keywords
POT1, Post-translational modifications, Unexpected molecular weights
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-214320 (URN)10.1016/j.dnarep.2013.08.014 (DOI)000327579200003 ()
Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2017-12-06Bibliographically approved
Põlajeva, J., Swartling, F., Jiang, Y., Singh, U., Pietras, K., Uhrbom, L., . . . Roswall, P. (2012). miRNA-21 is developmentally regulated in mouse brain and is co-expressed with SOX2 in glioma. BMC Cancer, 12, 378
Open this publication in new window or tab >>miRNA-21 is developmentally regulated in mouse brain and is co-expressed with SOX2 in glioma
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2012 (English)In: BMC Cancer, ISSN 1471-2407, E-ISSN 1471-2407, Vol. 12, p. 378-Article in journal (Refereed) Published
Abstract [en]

Background

MicroRNAs (miRNAs) and their role during tumor development have been studied in greatdetail during the last decade, albeit their expression pattern and regulation during normaldevelopment are however not so well established. Previous studies have shown that miRNAsare differentially expressed in solid human tumors. Platelet-derived growth factor (PDGF)signaling is known to be involved in normal development of the brain as well as in malignantprimary brain tumors, gliomas, but the complete mechanism is still lacking. We decided toinvestigate the expression of the oncogenic miR-21 during normal mouse development andglioma, focusing on PDGF signaling as a potential regulator of miR-21.

Methods

We generated mouse glioma using the RCAS/tv-a system for driving PDGF-BB expression ina cell-specific manner. Expression of miR-21 in mouse cell cultures and mouse brain wereassessed using Northern blot analysis and in situ hybridization. Immunohistochemistry andWestern blot analysis were used to investigate SOX2 expression. LNA-modified siRNA wasused for irreversible depletion of miR-21. For inhibition of PDGF signaling Gleevec(imatinib mesylate), Rapamycin and U0126, as well as siRNA were used. Statisticalsignificance was calculated using double-sided unpaired Student´s t-test.

Results

We identified miR-21 to be highly expressed during embryonic and newborn braindevelopment followed by a gradual decrease until undetectable at postnatal day 7 (P7), thiscorrelated with SOX2 expression. Furthermore, miR-21 and SOX2 showed up-regulation andoverlapping expression pattern in RCAS/tv-a generated mouse brain tumor specimens. Uponirreversible depletion of miR-21 the expression of SOX2 was strongly diminished in bothmouse primary glioma cultures and human glioma cell lines. Interestingly, in normalfibroblasts the expression of miR-21 was induced by PDGF-BB, and inhibition of PDGFsignaling in mouse glioma primary cultures resulted in suppression of miR-21 suggesting thatmiR-21 is indeed regulated by PDGF signaling.

Conclusions

Our data show that miR-21 and SOX2 are tightly regulated already during embryogenesisand define a distinct population with putative tumor cell of origin characteristics. We believethat miR-21 is a mediator of PDGF-driven brain tumors, which suggests miR-21 as apromising target for treatment of glioma.

Keywords
miRNA, miR-21, Glioma, PDGF-BB, SOX2, Imatinib (Gleevec), RCAS/tv-a
National Category
Biochemistry and Molecular Biology Cell Biology
Identifiers
urn:nbn:se:uu:diva-180243 (URN)10.1186/1471-2407-12-378 (DOI)000312098700001 ()
Available from: 2012-09-01 Created: 2012-09-01 Last updated: 2017-12-07Bibliographically approved
Singh, U., Sun, T., Looman, C., Heuchel, R., Elliott, R. W., Freichel, M., . . . Fundele, R. (2007). Expression and Function of the Gene Encoding the Voltage-Dependent Calcium Channel β3-Subunit in the Mouse Placenta. Placenta, 28(5-6), 412-420
Open this publication in new window or tab >>Expression and Function of the Gene Encoding the Voltage-Dependent Calcium Channel β3-Subunit in the Mouse Placenta
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2007 (English)In: Placenta, ISSN 0143-4004, E-ISSN 1532-3102, Vol. 28, no 5-6, p. 412-420Article in journal (Refereed) Published
Abstract [en]

Voltage-dependent Ca(2+) channels (VDCC) exist in most excitable cells and their properly regulated activity is essential for critical biological processes as many of these are sensitive to cellular Ca(2+) ion concentration. The ancillary cytoplasmic Ca(2+) channel beta subunits (CACNB) modulate Ca(2+) channel function and are required to enhance the number of functional channels in the plasma membrane. There are four genes encoding CACNB subunits and the gene encoding CACNB3 is over expressed in hyperplastic placentas of mouse interspecies hybrids. To determine the role of CACNB3 in the mouse placenta, we performed an expression and function analysis. Our results show that Cacnb3 exhibits specific spatial and temporal expression in the mouse placenta. Deletion of Cacnb3 does not produce a strong placental phenotype, which may be due to expression of other CACNB subunit encoding genes; however, sporadic occurrence of a labyrinthine architecture phenotype, characterized by reduced density of fetal blood vessels and decrease in pericyte number, could be observed. Down-regulation of Cacnb3 expression did not rescue placental hyperplasia in a model of interspecies hybrid placentas, which indicates that up-regulation in the hyperplastic placentas is a downstream event.

Keywords
Cacnb3, Spongiotrophoblast, Mouse placenta, Hyperplasia
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-94490 (URN)10.1016/j.placenta.2006.05.007 (DOI)000246449700007 ()16822546 (PubMedID)
Available from: 2006-05-08 Created: 2006-05-08 Last updated: 2017-12-14Bibliographically approved
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