Termination of a transcription unit comprising highly expressed genes in the archaebacterium Methanococcus voltae.

The 3'termini of transcripts originating from genes organized in a highly expressed transcription unit were analyzed in the archaebacterium Methanococcus voltae. The putative termination signals were found in an AT-rich intergenic region following the 3'-terminal gene. The two detected signals both contain oligo(T) sequences. A possible stem/loop structure immediately precedes one of the oligo(T) tracts. This secondary structure is considered to have an additional function in stabilizing the transcripts

Conserved elements in the transcription initiation regions preceding highly expressed structural genes of methanogenic archaebacteria.

The sequences of the intergenic regions of the strongly expressed genes encoding methyl CoM reductase in three different methanogenic archaebacteria were determined and the 5'-ends of the transcripts were mapped. After alignment, consensus sequences were found which are located both upstream and downstream of the transcription starts. They correspond, in part, to those previously characterized as putative elements of archaebacterial promoter sequences. In addition, bending of the DNA in front of the transcription start sites was shown in two cases and a characteristic common DNA structure immediately downstream of the 5'-end of the transcript was discovered. This structure was also found in the corresponding regions of previously described genes in methanogens. Our results suggest that both sequence and structural information may have roles in the initiation of transcription of protein encoding genes of these archaebacteria

A conjugation-like mechanism for prespore chromosome partitioning during sporulation in Bacillus subtilis

Spore formation in Bacillus subtilis begins with an asymmetric cell division that superficially resembles the division of vegetative cells. Mutations in the spoIIIE gene of B. subtilis partially block partitioning of one chromosome into the smaller (prespore) compartment of the sporulating cell. Point mutations that specifically block prespore chromosome partitioning affect a carboxy-terminal domain of SpoIIIE that shows significant sequence similarity to the DNA transfer (Tra) proteins of several conjugative plasmids of Streptomyces. In wild-type sporulating cells, the prespore chromosome passes through an intermediate stage resembling the state in which spoIIIE mutant cells are blocked. The prespore chromosome is then transferred progressively through the newly formed spore septum. We propose that translocation of the prespore chromosome occurs by a mechanism that is functionally related to the conjugative transfer of plasmid DNA