Current Issues in Molecular Biology

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Genome DNA Sequence Variation, Evolution, and Function in Bacteria and Archaea

by Hiromi Nishida

Curr. Issues Mol. Biol. 2013, 15(1), 19-24; https://doi.org/10.21775/cimb.015.019 - 6 Jul 2012

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Comparative genomics has revealed that variations in bacterial and archaeal genome DNA sequences cannot be explained by only neutral mutations. Virus resistance and plasmid distribution systems have resulted in changes in bacterial and archaeal genome sequences during evolution. The restriction-modification system, a virus resistance system, leads to avoidance of palindromic DNA sequences in genomes. Clustered, regularly interspaced, short palindromic repeats (CRISPRs) found in genomes represent yet another virus resistance system. Comparative genomics has shown that bacteria and archaea have failed to gain any DNA with GC content higher than the GC content of their chromosomes. Thus, horizontally transferred DNA regions have lower GC content than the host chromosomal DNA does. Some nucleoid-associated proteins bind DNA regions with low GC content and inhibit the expression of genes contained in those regions. This form of gene repression is another type of virus resistance system. On the other hand, bacteria and archaea have used plasmids to gain additional genes. Virus resistance systems influence plasmid distribution. Interestingly, the restriction-modification system and nucleoid-associated protein genes have been distributed via plasmids. Thus, GC content and genomic signatures do not reflect bacterial and archaeal evolutionary relationships. Full article

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MicroRNAs: Synthesis, Gene Regulation and Osteoblast Differentiation

by S. Vimalraj and N. Selvamurugan

Curr. Issues Mol. Biol. 2013, 15(1), 7-18; https://doi.org/10.21775/cimb.015.007 - 11 May 2012

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Abstract

The central dogma of transfer of genetic information from DNA to protein via mRNA is now challenged by small fragment of non coding RNAs typically 19-25 nucleotides in length namely microRNAs (miRNAs). miRNAs regulate expression of the protein coding genes by interfering in their mRNAs and, thus, act as key regulators of diverge cellular activities. Osteoblast differentiation, a key step in skeletal development involves activation of several signalling pathways including TGFb, BMP, Wnt and transcription factors, which are tightly regulated by miRNAs. In this review, we provide information on recent developments of the synthesis and gene regulation of miRNAs as well as the potential nature of miRNAs that regulate mesenchymal stem cell towards osteoblast differentiation for therapeutic purpose. Full article

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The Molecularly Crowded Cytoplasm of Bacterial Cells: Dividing Cells Contrasted with Viable but Non-culturable (VBNC) Bacterial Cells

by J. T. Trevors, J. D. van Elsas and A.K. Bej

Curr. Issues Mol. Biol. 2013, 15(1), 1-6; https://doi.org/10.21775/cimb.015.001 - 18 Apr 2012

Cited by 2 | Viewed by 571

Abstract

In this perspective, we discuss the cytoplasm in actively growing bacterial cells contrasted with viable but nonculturable (VBNC) cells. Actively growing bacterial cells contain a more molecularly crowded and organized cytoplasm, and are capable of completing their cell cycle resulting in cell division. In contrast, nutrient starving bacteria in the physiological VBNC state are struggling to survive, as essential nutrients are not available or limiting. The cytoplasm is not as molecularly crowded as gene expression is minimal (e.g., ribosome, transcript, tRNA and protein numbers are decreased), energy pools are depleted, cells may exhibit leakage, and DNA is not being replicated for cell division. Full article

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Curr. Issues Mol. Biol., Volume 15, Issue 1 (January 2013) – 3 articles

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