The first nucleotide of a transcribed DNA sequence where RNA polymerase (DNA-DIRECTED RNA POLYMERASE) begins synthesizing the RNA transcript.

Synonyms: Start Sites, Transcription, Sites, Transcription Initiation, Transcription Start Sites, Site, Transcription Start, Site, Transcription Initiation, Transcription Initiation Site, Sites, Transcription Start, Initiation Site, Transcription, Start Site, Transcription, Initiation Sites, Transcription, Transcription Start Site, Transcription Initiation Sites