Triple-helix structure in telomerase RNA contributes to catalysis

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Telomerase is a ribonucleoprotein (RNP) complex essential for replicating chromosome ends.
• Its RNA subunit acts as a template for telomeric DNA synthesis by the reverse-transcriptase (TERT) subunit.
• The RNA subunit also recruits other proteins to form the functional RNP complex.

Purpose of the Study:

• To investigate the role of a specific RNA structure in telomerase activity.
• To determine if a conserved triple helix within the telomerase RNA pseudoknot influences TERT binding or catalysis.
• To elucidate the mechanism by which RNA contributes to telomerase function.

Main Methods:

• Phylogenetic analysis of telomerase RNA sequences to identify conserved structures.
• Biochemical assays to assess telomerase activity in the presence or absence of specific RNA structural elements.
• Mutational analysis to probe the function of 2'-OH groups within the RNA triple helix.

Main Results:

• A phylogenetically conserved triple helix in the telomerase RNA pseudoknot is crucial for telomerase activity.
• This triple helix does not appear to bind the TERT protein.
• 2'-OH groups extending from the triple helix directly participate in the catalytic mechanism of both yeast and human telomerase.
• The RNA's catalytic role may involve orienting the primer-template, similar to group I ribozymes.

Conclusions:

• The RNA component of telomerase plays a direct catalytic role, independent of TERT binding.
• The findings suggest that RNA's involvement in telomerase catalysis is a key feature of its function.
• Telomerase may represent an evolutionary link between RNA enzymes (ribozymes) and RNP enzymes, with its RNA catalytic role potentially acquired later in evolution or conserved from an ancient RNA-based system.