Many retailers have opened up self-service checkout lanes lately, which are great for those customers with just a few items, or don’t want to get stuck behind the old couple who still pays with paper checks. According to a recent report, when it comes to transcription, at least some miRNAs might have the option to use a similar, Self-Service Transcription shortcut.
Researchers from Rhode Island and Miriam Hospitals discovered a new and atypical mode of transcription that involves self transcription small, transfected DNA fragments containing a miRNA precursor (pre-miRNA) sequence, without an exogenous promoter. The team first noticed this phenomenon when a “negative control” they were using for their miRNA expression vector experiments, consisting of just a transfected, PCR amplified, miRNA gene fragment (AMPmiRNA-143), led to some positive results (i.e. expression of mature miR-143). This of course piqued their curiosity, and led them to explore what was going on. The scientists found out that:
- AMPmiRNA-143 was being self transcribed without a RNAP II/III promoter.
- The minimum fragment size needed for AMPmiRNA-143 to generate a mature miRNA is 102nt.
- Atypical transcription occurs in several cell types; although it’s difficult to see in those with already high expression of your target miRNA.
- The self transcribed mature miRNAs are functional.
- Knockdown of RNAP I, II and III did not reduce self transcription.
- Transfection of AMPmiRNA-143 did not seem to effect endogenous miRNA expression
The Rhode Island researchers are still searching for the secrets behind this new transcription mechanism. In the meantime this report has left the EpiGenie team with enough questions to keep our wheels turning for quite a while. Get in the Self-Serve Checkout lane for all the details at Nucleic Acids Research, January 2010