This topic is so mind-boggling and fascinating — that I’d like to send David Nelson’s email blog, just as it was received. Fusarium species are ubiquitous filamentous fungi, found in virtually any soil, in the air, and on plants. They are most commonly associated with cereal crops and grain dust (e.g., rye, barley, corn, oats and buckwheat). CYP621A is a plant cytochrome P450 gene located in Family 621, subfamily A. This fungus can cause human infections.
For those of us who have done genomic DNA sequencing and searching for introns, we know that donor sites and acceptor sites (which are recognized by the spliceosome machinery) are conserved, boundary sequences at the 5′ and 3′ ends of an intron, respectively. These sites guide the spliceosome to excise the intron and ligate the adjacent exons. The donor site (5′ splice site) marks the start of the intron, typically with a GU (in the RNA), or GT (in the DNA) sequence. The acceptor site (3′ splice site) marks the end, usually with an AG sequence.
Some of us have heard of a single triplet codon comprising the entire exon (e.g., GTCGCAG where CGC codes for the amino acid arginine), but the recent publication by David Nelson describes a single nucleotide (GTAAG in which the “A” is located as the middle nucleotide of a triplet codon) that represents the entire exon(!!). Possible reasons for such a genomics structure are discussed in his paper. [For several unusual stories of gene structure and genomics posted each week, you are encouraged to sign up/subscribe at https://substack.com/@davidrnelson] 😊
DwN