Temozolomide Induces Aberrant RNA Alkylation and Widespread Translational Repression

Temozolomide (TMZ), a key alkylating chemotherapy, has direct effects on RNA modifications and translation dynamics that are not well understood. This study reveals that TMZ causes widespread RNA alkylation and severe translation impairment. In test tubes, TMZ deposits abnormal methyl groups onto single-stranded mRNA, forming physical damage that reduces translation efficiency.

When glioblastoma cells are exposed to acute TMZ, they quickly show a large increase in m7G on cellular RNAs, resulting in significant reduction of overall protein synthesis. Using nanopore direct RNA sequencing, the study identified specific guanine-specific error patterns and sequence context preferences related to TMZ-induced damage.

Applying a quantitative yeast spike-in ribosome profiling approach, the researchers mapped this translational repression at the transcript level, finding a global drop in translation efficiency. This widespread repression particularly affects highly interconnected networks crucial for cellular growth, especially those involved in chromosome organization.

The study suggests that the extent of this translational repression depends on the guanine density, stability and translation initiation speed of the RNA. Overall, these results indicate that TMZ-induced alkylation targets stable, highly translated, guanine-rich transcripts, establishing abnormal RNA methylation and subsequent translation arrest as a possible cause of temozolomide's toxic effects.