Mitochondrial transcription: how does it end?

Abstract

The structure of the mitochondrial transcription termination factor (MTERF1) provides novel insight into the mechanism of binding, recognition of the termination sequence and the conformational changes involved in mediating termination. Besides its functional implications, this structure provides a framework to understand the consequences of numerous diseases associated with mitochondrial DNA mutations.

Keywords: MTERF; POLRMT; base-flipping; gene expression; mitochondria; mitochondrial transcription termination; polarity.

Figure 1

(A) Structure of the mitochondrial transcription termination factor MTERF1 (blue) bound to the leu-tRNA mitochondrial DNA termination sequence (red). (B) Stacking interactions with MTERF1 residues (blue) stabilize three DNA bases (purple) in an extrahelical position. The molecular surface is transparent.

Figure 2

(A) E. coli replication is terminated when the helicase DnaB (orange), is blocked by termination factor Tus (blue). (B) MTERF1 (green) may interact with POLRMT (red) and mediate transcription termination. Specific protein-protein interactions might explain termination polarity. (C) A hairpin loop is formed in the nascent RNA (black) terminating transcription in a mechanism similar to rho-independent termination, destabilizing the RNAP—RNA interaction. Large arrows indicate direction of transcription. (D) Mitochondrial RNA polymerase (POLRMT-red) terminates transcription via the formation of a G-quadruplex structure in the nascent RNA (black) in a mechanism similar to the termination process shown in (C).