Genes for a nuclease and a protease are involved in the drastic decrease in cellular RNA amount in fission yeast...

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Cellular RNA levels decrease significantly in Schizosaccharomyces pombe during nitrogen starvation.
• A previously identified soluble RNA-degrading enzyme, a nuclease encoded by pnu1(+), showed increased activity under nitrogen starvation.

Purpose of the Study:

• To investigate the role of the Pnu1 nuclease in the reduction of cellular RNA during nitrogen starvation.
• To elucidate the regulatory mechanisms controlling the RNA-degrading activity of Pnu1.

Main Methods:

• Comparison of RNA-degrading activity and cellular RNA levels in wild-type and pnu1 null-mutant (pnu1Δ) S. pombe cells under nitrogen starvation.
• Analysis of the dependence of Pnu1 activity on the Wis1 MAP kinase cascade and Tor1 signaling pathway.
• Examination of the role of isp6(+) in RNA degradation by studying an isp6 null-mutant (isp6Δ).

Main Results:

• pnu1Δ cells exhibited no significant increase in RNA-degrading activity and only a slight decrease in cellular RNA during nitrogen starvation, unlike wild-type cells.
• The increased RNA-degrading activity in wild-type cells was independent of the Wis1 and Tor1 pathways.
• The activity was strongly dependent on isp6(+), with isp6Δ mutants showing deficiencies in both increased RNA-degrading activity and significant RNA reduction.

Conclusions:

• Pnu1 nuclease plays a crucial role in the substantial decrease of cellular RNA during nitrogen starvation in S. pombe.
• The protease isp6(+) is involved in regulating Pnu1's RNA-degrading activity, thus contributing to nitrogen starvation-induced RNA reduction.