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. 2024 Jun 28;15(8):e01021-24. doi: 10.1128/mbio.01021-24

Fig 1.

Pathway diagram of nucleotide metabolism depicts the conversion of IMP to XMP and adenylosuccinate, leading to GMP and AMP, and further to GTP and ATP. It includes details on gene regulation via GTP concentration affecting transcription start sites.

IMD2 mRNA synthesis is regulated by GTP-dependent start site selection and transcriptional attenuation. Imd2 catalyzes the first committed step of GTP synthesis from IMP, which is also a precursor of ATP. IMD2 has multiple transcription start sites (TSS, bent arrows). Upstream TSS are used when cellular GTP is sufficient, producing transcripts containing a Nrd1-Nab3-Sen1 (NNS) terminator that terminate prematurely and are degraded by the nuclear exosome. When cellular GTP is deficient, a downstream TSS is preferentially used, resulting in full-length mRNA [adapted from reference (8)].