GAAC element

The GAAC element is usually a core promoter element containing guanine (G), adenine (A), and cytosine (C), able to direct a new transcription start site 2-7 base pairs (bp)s downstream of itself.
This element also controls the rate of transcription initiation and interacts in a sequence-specific manner with the transcription factor II D (TFIID) complex. CpG islands typically occur at or near the transcription start site of genes, particularly housekeeping genes, in vertebrates. Normally a C (cytosine) base followed immediately by a G (guanine) base (a CpG) is rare in vertebrate DNA because the cytosines in such an arrangement tend to be methylated.
Collagen Type I, alpha 1 promoter
The genes encoding type I collagen chains are selectively activated in fibroblasts and osteoblasts within the promoter by a sequence between -3.2 and -2.3 kb. Two short elements (tendon-specific element 1, TSE1, and 2, TSE2) within this sequence are necessary to direct gene expression.<ref name=Terraz/> The binding sequence of TSE2 is an E-box. TSE1 and TSE2 need to cooperate with each other and other cis-acting elements of the proximal promoter to activate gene expression.<ref nameTerraz/> A short sequence in TSE1 contains a 5'-GAACT-3' motif that binds a tendon-specific nuclear protein.<ref nameTerraz/>

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