The Evolutionary Significance of Small Nuclear RNAs (Campbell Biology)
Small nuclear RNAs can regulate gene expression at multiple steps and in many ways. While this section has focused on ncRNAs in eukaryotes, small ncRNAs are also used by bacteria as a defense system, called the CRISPR-Cas9 system, against viruses that infect them. The use of ncRNAs thus evolved long ago, but we don’t yet know how bacterial ncRNAs are related to those of eukaryotes.
What about the evolutionary significance of small eukaryotic ncRNAs? In general, extra levels of gene regulation might allow evolution of a higher degree of complexity of form. The versatility of micro RNA regulation has therefore led some biologists to hypothesize that an increase in the number of different miRNAs specified by the genome of a given species has allowed morphological complexity to increase over evolutionary time. While this hypothesis is still being evaluated, it is logical to expand the discussion to include all small ncRNAs. Exciting new techniques for rapidly sequencing genomes have allowed biologists to begin asking how many genes for ncRNAs are present in the genome of any given species. A survey of different species supports the notion that small interfering RNAs evolved first, followed by miRNAs and later piwi-interacting RNAs, which are found only in animals. And while there are hundreds of types of miRNAs, there appear to be 60,000 or so types of piRNAs, allowing the potential for very sophisticated gene regulation by piRNAs.
Given the extensive functions of ncRNAs, it is not surprising that many of the ncRNAs characterized thus far play important roles in embryonic development. Embryonic development is perhaps the ultimate example of precisely regulated gene expression.
Urry, Lisa A.. Campbell Biology. Pearson Education. Kindle Edition. https://www.pearson.com/us/higher-education/series/Campbell-Biology-Series/2244849.html
Research Article: Ancient Origin of the U2 Small Nuclear RNA Gene-Targeting Non-LTR Retrotransposons Utopia
Date Published: November 10, 2015 Publisher: Public Library of Science Author(s): Kenji K. Kojima, Jerzy Jurka, Jürgen Schmitz. http://doi.org/10.1371/journal.pone.0140084 Abstract: Most non-long terminal repeat (non-LTR) retrotransposons encoding a restriction-like endonuclease show target-specific integration into repetitive sequences such as ribosomal RNA genes and microsatellites. However, only a few target-specific lineages of non-LTR retrotransposons are distributed widely … Continue reading
Date Published: June 12, 2013 Publisher: Public Library of Science Author(s): Olga Pontes, Alexa Vitins, Thomas S. Ream, Evelyn Hong, Craig S. Pikaard, Pedro Costa-Nunes, Eric Jan. http://doi.org/10.1371/journal.pone.0065652 Abstract: In Arabidopsis thaliana, functionally diverse small RNA (smRNA) pathways bring about decreased RNA accumulation of target genes via several different mechanisms. Cytological experiments have suggested that the … Continue reading
Research Article: New Small Nuclear RNA Gene-Like Transcriptional Units as Sources of Regulatory Transcripts
Date Published: February 2, 2007 Publisher: Public Library of Science Author(s): Aldo Pagano, Manuele Castelnuovo, Federico Tortelli, Roberto Ferrari, Giorgio Dieci, Ranieri Cancedda, Lisa Stubbs Abstract: By means of a computer search for upstream promoter elements (distal sequence element and proximal sequence element) typical of small nuclear RNA genes, we have identified in the human … Continue reading
Research Article: Deep Sequencing of Human Nuclear and Cytoplasmic Small RNAs Reveals an Unexpectedly Complex Subcellular Distribution of miRNAs and tRNA 3′ Trailers
Date Published: May 14, 2010 Publisher: Public Library of Science Author(s): Jian-You Liao, Li-Ming Ma, Yan-Hua Guo, Yu-Chan Zhang, Hui Zhou, Peng Shao, Yue-Qin Chen, Liang-Hu Qu, Shuang-yong Xu. http://doi.org/10.1371/journal.pone.0010563 Abstract: MicroRNAs (miRNAs) are ∼22-nt small non-coding regulatory RNAs that have generally been considered to regulate gene expression at the post-transcriptional level in the cytoplasm. However, … Continue reading
Research Article: Alternative Processing of the U2 Small Nuclear RNA Produces a 19–22nt Fragment with Relevance for the Detection of Non-Small Cell Lung Cancer in Human Serum
Date Published: March 20, 2013 Publisher: Public Library of Science Author(s): Julien Mazières, Caroline Catherinne, Olivier Delfour, Sandrine Gouin, Isabelle Rouquette, Marie-Bernadette Delisle, Grégoire Prévot, Roger Escamilla, Alain Didier, David H. Persing, Mike Bates, Bernard Michot, Liang-Hu Qu. http://doi.org/10.1371/journal.pone.0060134 Abstract: RNU2 exists in two functional forms (RNU2-1 and RNU2-2) distinguishable by the presence of a unique … Continue reading