Chapter 4 - Families of DNA binding transcription factors

Abstract

This chapter focuses on a number of different DNA binding motifs, common to several different transcription factors, which can mediate DNA binding. It is also possible for the same DNA sequence to be bound by more than one factor. Although in many cases, the factors binding to a particular DNA sequence share a common DNA binding domain, this is not always the case. Thus, whilst the transcription factors CTF/NFI and C/EBP both bind to the CAAT box sequence, they do so via completely different DNA binding domains, with C/EBP having a basic DNA binding domain whilst CTF/NFI has a DNA binding domain distinct from that of any other factor. It is unlikely therefore that the existence of several distinct DNA binding domains reflects the need of the factors which contain them to bind to distinct types of DNA sequences. Rather, it seems perfectly possible that one DNA binding motif could be present in all factors with variations of it in different factors producing the observed binding to different DNA sequences. This is particularly so in view of the fact that in diverse DNA binding motifs such as the helix-turn-helix, the basic DNA binding domain and the two types of zinc fingers, the amino acids which determine sequence specific binding to DNA are all located within similar alphahelical structures.