Nuclear Retention of mRNA in Mammalian Tissues

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Messenger RNA (mRNA) is traditionally considered to function primarily in the cytoplasm.
• Nuclear retention of mRNA is a known regulatory mechanism but is thought to be rare in mammals.
• The extent of mRNA nuclear localization in metabolic tissues remains largely unexplored.

Purpose of the Study:

• To investigate the prevalence and functional significance of mRNA nuclear retention in mammalian metabolic tissues.
• To challenge the established view of mRNA's predominantly cytoplasmic localization.
• To explore the nucleus's role in regulating gene expression noise.

Main Methods:

• Combined deep sequencing of nuclear and cytoplasmic RNA fractions.
• Employed single-molecule transcript imaging.
• Studied mouse beta cells, liver, and gut tissues.

Main Results:

• Identified a broad spectrum of protein-coding genes with higher spliced, polyadenylated mRNA levels in the nucleus compared to the cytoplasm.
• Observed nuclear retention for key metabolic genes, including transcription factor ChREBP, Nlrp6, Glucokinase, and Glucagon receptor.
• Demonstrated that nuclear mRNA retention effectively buffers cytoplasmic transcript levels against transcriptional burst noise.

Conclusions:

• Nuclear retention of mRNA is a significant phenomenon in mammalian metabolic tissues, contrary to previous assumptions.
• The nucleus plays a crucial role in dampening gene expression noise by retaining mRNA.
• This finding redefines our understanding of mRNA localization and gene expression regulation.