EXPRESSION OF CONJUGATION GENES IS CONTROLLED BY PROCESSIVE ANTITERMINATION AND A NOVEL ZIPPER-TYPE TRANSCRIPTIONAL...

Area of Science:

• Bacterial genetics
• Molecular biology
• Gene regulation

Background:

• Large operons, such as the conjugation operon in Bacillus subtilis plasmid pLS20, require complex regulatory mechanisms for proper gene expression.
• The pLS20 conjugation operon is over 32 kb long and initiates with a leader region preceding genes for a two-component antitermination system.

Purpose of the Study:

• To identify and characterize regulatory elements within the leader region of the Bacillus subtilis pLS20 conjugation operon.
• To elucidate the mechanism of transcriptional attenuation controlling the expression of this large operon.

Main Methods:

• In vivo and in vitro analyses were employed to study the transcriptional attenuator.
• Structural analysis involved identifying stem-loop formations and complementary sequences within the leader region.

Main Results:

• A novel transcriptional attenuator, named cATTpLS20, was identified in the 456 nt leader region of the pLS20 conjugation operon.
• cATTpLS20 features a zipper-type structure, with complementary sequences enabling a switch between attenuator and antiterminator conformations.
• This zipper-type attenuator is conserved in related plasmids and other conjugative plasmids in Gram-positive bacteria.

Conclusions:

• The identified zipper-type attenuator, cATTpLS20, plays a crucial role in regulating the expression of the large pLS20 conjugation operon.
• This mechanism likely represents a common strategy for controlling gene expression in numerous conjugative plasmids within Gram-positive bacteria.