Junk DNA

My book manuscript has been reviewed by some outside experts and they seem to have convinced my editor that my book is worth publishing. I hope we can get it finished soon. It would be nice to publish in in September on the 10th anniversary of the ENCODE disaster.

Meanwhile, I keep scanning the literature for mentions of junk DNA to see if scientists are finally coming to their senses. Apparently not, and that's a good thing because it means that my book is still needed. Here's the opening paragraph from a recent review of lncRNAs. The authors are in the Department of Medicine at the Medical College of Gerogia, in Augusta, Georgia (USA).

Ghanam, A.R., Bryant, W.B. and Miano, J.M. (2022) Of mice and human-specific long noncoding RNAs. Mammalian Genome:1-12. [doi: 10.1007/s00335-022-09943-2]

Approximately ninety-eight percent of our genome is noncoding. Contrary to initial descriptions of this vast sea of sequence comprising “junk DNA” (Ohno 1972), comparative genomics and various next-generation sequencing studies have revealed millions of transcription factor binding sites (TFBS) (Vierstra et al. 2020) and tens of thousands of noncoding genes, most notably the class of long noncoding RNAs (LncRNAs), defined currently as processed transcripts of length > 200 base pairs with no protein-coding capacity (Rinn and Chang 2020; Statello et al. 2021). The widespread transcription of LncRNAs and abundance of regulatory sequences such as enhancers support the concept of a genome that is largely functional (ENCODE Project Consortium 2012). Such a dynamic genome should not be surprising given the complex nature of gene expression and gene function necessary for embryonic and postnatal development as well as disease processes.

• No reasonable scientist, especially Susumu Ohno, ever said that all noncoding DNA was junk.
• There are millions of transcription factor binding sites but most of them are spurious binding sites that have nothing to do with regulation. They simply reflect the expected behavior of typical DNA binding proteins in a large genome full of junk DNA.
• Nobody has demonstrated that there are tens of thousand of noncoding genes. There may be tens of thousands of transcripts but that's not the same thing since you have to prove that those transcripts are functional before you can say that they come from genes.
• There is currently no evidence to support the concept of a genome that is largely functional in spite of what the ENCODE researchers might have said ten years ago.
• Such a genome would be very surprising, if it were true, given what we know about genomes, evolution, and basic biochemistry.

Except for those few minor details—I hope I'm not being too picky—that's a pretty good way to start a review of lncRNAs. :-)

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