RNA recognition by the DNA end-binding Ku heterodimer.

Nucleic acid-binding proteins typically interact with either DNA or RNA, but not both. Ku heterodimers are distinct in their dual capacity to bind DNA and RNA. Ku is known for its role in DNA repair and telomere maintenance. It binds DNA ends in a sequence-independent manner. However, Ku also interacts with RNA, particularly the TLC1 subunit of telomerase. This RNA binding is essential for the enzyme's nuclear localization. The mechanisms behind RNA recognition by Ku remain unclear. Prior research has focused on DNA interactions. Little is known about the RNA features that allow Ku to bind. This gap motivated a detailed investigation into the RNA-binding properties of Ku.

This study aimed to understand how Ku recognizes RNA. The focus was on the TLC1 RNA hairpin. The researchers wanted to identify the RNA elements that enable Ku binding. They used phosphorothioate footprinting to pinpoint the binding site. Chemical modification helped reveal an unexpected motif. Mutagenesis experiments tested the importance of specific RNA elements. The goal was to determine the structural requirements for Ku-RNA interaction. The study also examined whether this RNA-binding function is conserved. The findings could clarify the dual role of Ku in DNA and RNA biology.

The researchers used phosphorothioate footprinting to locate the Ku-binding site on TLC1 RNA. They achieved single-nucleotide resolution with this technique. Chemical modification was applied to identify a hidden motif in the RNA structure. Mutagenesis experiments altered the RNA to test binding requirements. The team analyzed the effects of these mutations on Ku interaction. They compared wild-type and mutant RNA binding to Ku. The study also examined other budding yeast telomerase RNAs. The presence of the Ku-binding site in these RNAs was assessed.

The Ku-binding site on the TLC1 hairpin was mapped with high precision. A specific motif within the RNA secondary structure was identified. This motif was not predicted by existing models. Mutagenesis confirmed the importance of this motif for Ku binding. The RNA hairpin structure is critical for interaction. The study showed that DNA and RNA binding by Ku are mutually exclusive. Evidence was found for the Ku-binding site in other yeast telomerase RNAs. These findings suggest that RNA binding may be a conserved function of Ku.

The study provides insights into how Ku recognizes RNA. The RNA hairpin motif is essential for Ku binding. The findings suggest that RNA binding is a conserved feature of Ku. The researchers found evidence of the binding site in other yeast telomerase RNAs. This supports the idea that RNA recognition is not limited to TLC1. The study highlights the structural requirements for Ku-RNA interaction. The results are consistent with the authors' hypothesis. The authors propose that RNA binding plays a broader role in Ku function.