What is it about?
Same-nucleotide repeats (iterons) are quite frequent in DNAs and RNAs. Guanine (G) and cytosine (C) iterons, as well as the strings of both G and C nucleotides, produce stable complexes between RNAs (as well as between RNAs and proteins) but were not studied for microRNAs (miRs), small RNAs that regulate the protein-coding messenger RNAs (mRNAs). The iterons and strings may differ in the four principal groups of miRs, the structurally matched 5p and 3p, and the unmatched 5n and 3n miRs (the '5' and '3' indicating origin in the first and second half of microRNA precursors).This work therefore quantified the G and C iterons and the GC strings in these subgroups of human miRs.
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Why is it important?
We found that 5p miRs have significantly more G iterons than other miR groups, and the 3p miRs have an inverse excess of C iterons. The 5n and 3n miRs (which lack functional counter-stems) both have a large number of G iterons. In all miR subgroups the contiguous GC strings constitute a larger part of sequences than the AU strings. A surplus of G or C iterons and of GC strings should enable a more stable association with the target mRNAs. The G iterons should be also important in association with proteins.
Perspectives
The miRs researched thus far have a large bias for those described before 2008 (and constituting less than 20% of miRs recognized in 2018). The researched miRs tend to be poor in G and C iterons and in the GC strings, and have lower affinity for mRNAs as a class (or for many types of RNA-binding proteins) than is found for post-2008 miRs as a class. It is important to research the RNA and protein binding of, and co-regulation by, G/C iteron-rich and GC string-rich miRs regardless of the year of introduction.
Prof. Steven L Parker
UTHSC Memphis
Read the Original
This page is a summary of: G and C Iterons and Strings in MicroRNAs Should be Important in Regulation of mRNAs†, MicroRNA, January 2016, Bentham Science Publishers,
DOI: 10.2174/2211536604666151015093749.
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