SmD3 regulates intronic noncoding RNA biogenesis

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Excess lipid accumulation in nonadipose tissues contributes to oxidative stress, organ dysfunction, and diabetic complications.
• Previous studies identified small nucleolar RNAs (snoRNAs) as mediators of lipotoxic cell death under conditions of metabolic stress.

Purpose of the Study:

• To identify novel molecular mechanisms underlying lipotoxicity and cellular response to metabolic stress.
• To investigate the role of spliceosomal protein SmD3 in regulating noncoding RNA processing and its contribution to lipotoxicity.

Main Methods:

• Retroviral promoter trap mutagenesis was employed to generate mutant Chinese hamster ovary (CHO) cell lines resistant to lipotoxic and oxidative stress.
• Characterization of a novel SmD3 haploinsufficiency mutant to assess its impact on snoRNA expression and pre-mRNA splicing.

Main Results:

• A novel mutant with disrupted SmD3 gene demonstrated reduced snoRNA expression and abundance of snoRNA-containing intron lariats.
• SmD3 haploinsufficiency did not impede pre-mRNA splicing but affected small nuclear RNAs (snRNAs) U4 and U5 levels.
• SmD3 was implicated as a critical regulator of intronic noncoding RNA processing and a mediator of metabolic stress response pathways.

Conclusions:

• SmD3 plays a crucial role in the processing of intronic noncoding RNAs, particularly snoRNAs.
• Regulation of snoRNA expression by SmD3 links splicing machinery to cellular metabolic stress responses.
• This study identifies SmD3 as an upstream mediator in pathways combating lipotoxicity and associated organ dysfunction.