DragonRNA: Generality of DNA-primed RNA-extension activities by DNA-directed RNA polymerases

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• RNA polymerases (RNAPs) are enzymes responsible for transcribing DNA into RNA.
• Previous studies showed some RNAPs can add ribonucleotides to DNA 3' ends.
• Mitochondrial RNAPs (mtRNAPs) are essential for mitochondrial gene expression.

Purpose of the Study:

• To investigate the activity of mtRNAPs on DNA molecules with free 3' ends.
• To characterize the products formed by mtRNAP activity.
• To determine if this activity is a general property of various RNAPs.

Main Methods:

• Enzymatic assays using yeast and human mtRNAP preparations.
• Analysis of reaction products from diverse DNA oligonucleotide inputs.
• Development of fluorescence-based assays for product detection.

Main Results:

• Yeast and human mtRNAPs robustly extend DNA 3' ends with ribonucleotides.
• The resulting molecules are serial DNA→RNA chains, with DNA as the 5' end and RNA as the 3' end.
• This DNA 3'-end extension activity is a general property of various RNAPs, including phage and E. coli RNAP.

Conclusions:

• DNA can serve as both primer and template for ribonucleotide addition by RNAPs.
• A novel class of DNA→RNA molecules, termed DragonRNA, is formed through this process.
• This activity represents a fundamental capability of diverse RNA polymerases.