Human and human-yeast chimeric U6 snRNA genes identify structural elements required for expression in yeast

Area of Science:

• Molecular Biology
• Genetics
• RNA Biology

Background:

• U6 is a highly conserved spliceosomal small nuclear RNA (snRNA) crucial for splicing.
• Essential residues are concentrated in a 35-nucleotide region, including the U4-interaction domain.
• Despite 80% sequence identity, human U6 RNA cannot functionally replace yeast U6 RNA in vivo.

Purpose of the Study:

• To investigate the functional incompatibility of human U6 snRNA in yeast.
• To identify regions of the human U6 gene responsible for its inability to function in yeast.
• To explore the potential for domain-specific functional complementation between human and yeast U6 genes.

Main Methods:

• Construction and analysis of human-yeast chimeric U6 genes.
• Assessment of transcription and function of chimeric genes in yeast.
• Site-directed mutagenesis and promoter element analysis.

Main Results:

• The human U6 gene is not transcribed in yeast without specific promoter elements.
• Introduction of a yeast promoter element stimulates transcription but not function of the human U6 gene.
• The 5' domain and 3' terminal region of the human U6 gene can individually complement yeast U6.
• A chimera combining both the 5' and 3' functional domains of human U6 in yeast is lethal.

Conclusions:

• Functional incompatibility of human U6 snRNA in yeast is not due to a single domain.
• Specific domains of human U6 can be functionally replaced by yeast counterparts.
• Combinatorial interactions between human U6 domains lead to lethality in yeast, suggesting complex regulatory or structural incompatibilities.