Hudeček O, Benoni R, Reyes-Gutierrez PE, Culka M, Šanderová H, Hubálek M, Rulíšek L, Cvačka J, Krásný L, Cahová H.

Nat Commun. 2020 Feb 26;11(1):1052. doi:10.1038/s41467-020-14896-8

Dinucleoside polyphosphates act as 5'-RNA caps in bacteria.

T7 RNAP and E. coli RNAP efficiently initiate transcription with N(p)nN cap analogs at mM concentrations. LC-MS analysis of sRNAs digested with Nuclease P1 detects N(p)nN caps. Existence of the internal polyphosphate chain demonstrated by the fact that the N(p)nN caps are not fragmented by ionization, like GppppG and unlike pppGpG. m7Gp4Gm and m6Ap3A were further identified using synthetic standards. The RppH and ApaH enzymes cleaved caps, leaving 5′-p or 5′-ppp ends respectively. Cap methylation protects from RppH cleavage but not from ApaH.