DSSR-PyMOL cartoon-block schematics: PDB entry 7eh2

PDB-id

7eh2; DSSR-derived features in text and JSON formats

Class

transcription-DNA-RNA

Method

X-ray (3.34 Å)

Summary

Thermus thermophilus transcription initiation complex containing a template-strand pyrimidine at position tss-2 and gpg RNA primer

Reference

Skalenko KS, Li L, Zhang Y, Vvedenskaya IO, Winkelman JT, Cope AL, Taylor DM, Shah P, Ebright RH, Kinney JB, Zhang Y, Nickels BE (2021): "Promoter-sequence determinants and structural basis of primer-dependent transcription initiation in Escherichia coli ." Proc.Natl.Acad.Sci.USA, 118. doi: 10.1073/pnas.2106388118.

Abstract

Chemical modifications of RNA 5'-ends enable "epitranscriptomic" regulation, influencing multiple aspects of RNA fate. In transcription initiation, a large inventory of substrates compete with nucleoside triphosphates for use as initiating entities, providing an ab initio mechanism for altering the RNA 5'-end. In <i>Escherichia coli</i> cells, RNAs with a 5'-end hydroxyl are generated by use of dinucleotide RNAs as primers for transcription initiation, "primer-dependent initiation." Here, we use massively systematic transcript end readout (MASTER) to detect and quantify RNA 5'-ends generated by primer-dependent initiation for ∼4₁₀ (∼1,000,000) promoter sequences in <i>E. coli</i> The results show primer-dependent initiation in <i>E. coli</i> involves any of the 16 possible dinucleotide primers and depends on promoter sequences in, upstream, and downstream of the primer binding site. The results yield a consensus sequence for primer-dependent initiation, Y_TSS-2N_TSS-1N_TSSW_TSS+1, where TSS is the transcription start site, N_TSS-1N_TSS is the primer binding site, Y is pyrimidine, and W is A or T. Biochemical and structure-determination studies show that the base pair (nontemplate-strand base:template-strand base) immediately upstream of the primer binding site (Y:R_TSS-2, where R is purine) exerts its effect through the base on the DNA template strand (R_TSS-2) through interchain base stacking with the RNA primer. Results from analysis of a large set of natural, chromosomally encoded <i>E</i> <i>coli</i> promoters support the conclusions from MASTER. Our findings provide a mechanistic and structural description of how TSS-region sequence hard-codes not only the TSS position but also the potential for epitranscriptomic regulation through primer-dependent transcription initiation.