["Cis" and "trans" regulator elements of transcription].

The 5'-flanking region of genes is involved in transcription regulaton. Multiple nucleotidic cis-acting sites are spread out over a region of 400 bp, (mostly) upstream of the start point. Examples are given with TATA box, GC box, CCAAT box and some octamers. Transcription factors recognize cis-acting sites and bind to them. Some are required for transcription initiation. Others affect (usually enhance) the rate of initiation. Trans-regulator proteins contain two domains. One is responsible for binding to DNA (as for instance: Zn fingers, Leu zipper, positive homeotic domain). The other one is responsible for activity on transcription (as for instance: rich in Gln, rich in Pro, acidic alpha-helix domain). Some technics used for determination of the site of transcription initiation and of protein fixation on DNA are briefly described. It is hoped that a better comprehension of transcription mechanisms will offer new possibilities of investigation for acting in some varieties of protein synthesis dysfunctionnements.