Genome complexity: preparing for mRNA (Introduction)

by David Turell , Thursday, September 05, 2019, 01:58 (1695 days ago) @ David Turell

How the genome prepares for pre-mRNA splicing:

https://phys.org/news/2019-09-key-pre-mrna-splicing.html

"The study focuses on the pre-mRNA (precursor-messenger RNA) splicing process where regions in the pre-mRNA that do not encode proteins (referred to as introns) are removed by the spliceosome, a huge protein-RNA complex. Remaining sections of the RNA transcript, called exons, are then stuck back together. Pre-mRNA splicing is one of several essential steps that convert pre-mRNAs into mature mRNA (messenger RNA) for protein production.

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"How the pre-mRNA splicing process works is still subject to intense investigation by scientists. Specifically, the mechanisms of how introns and exons are defined in a sea of pre-mRNAs and how circular RNAs are generated by a particular back-splicing process are fundamental unanswered questions in pre-mRNA splicing. Through their experiments, Zhao and her colleagues proposed a unified model explaining all three phenomena (intron definition, exon definition, and back-splicing) without the need of a different spliceosome for each process, that are supported by their extensive biochemical experiments.

"'Splicing of pre-mRNA is essential for gene expression in all eukaryotes," Zhao said. "In higher eukaryotes such as mammals, an average of 95 percent of the nucleotides in the primary transcript of a protein-encoding gene are introns. These introns need to be precisely removed by splicing before the mRNA can be transported out of the nucleus and translated. Even a single nucleotide error can cause catastrophic consequences. It has also become increasingly clear that alternative splicing is a fundamental approach for eukaryotic gene expression regulation.'"

Comment: Chop it up, spit it out and start all over again. The genome are extremely complex and to work properly had to be designed in just the right way. It isn't just simple instructions. Bits and pieces have to be put together in a meaningful way. How do the protein molecules know what they are doing as they slice up DNA? Not by Darwin.