Step 1: Gene expression needs two kinds of DNA signals: ones that control how much a gene is expressed (TATA box, CAAT box, GC box, all promoter elements that help recruit transcription machinery) and ones that fix exactly where reading of the sequence should begin.
TATA box sets the position for transcription start indirectly by placing RNA polymerase correctly, CAAT box and GC box boost transcription efficiency, but the actual site read as the beginning of the message is defined by the initiation sequence.
This is why translation always begins at a defined initiation codon region and transcription begins at a defined initiation site, both covered under the general term initiation sequence.