Multiple RIP140 promoters have been identified and alternative splicing yields multiple RIP140 transcripts [25], [26], [28].
Intron-mediated enhancement of gene expression has been shown in a number of plant species [ 44, 52], and multiple ubiquitin promoters have shown enhanced transgene expression when the intron is included in the promoter region [ 19, 44- 46, 53, 54].
(C ) To reduce the requirement for multiple promoters, studies have shown that more than one guide RNAs can be expressed from a single promoter in various ways (Tsai et al., 2014 ; Nissim et al., 1016 ).
Once a regulator is coupled to multiple promoters that have different desired expression levels, there is no way that the regulator can adapt its activities to correlate highly with the desired levels of all its targets, and such regulators will experience selection to become more noisy.
Many promoters have multiple runs of G-residues, including those with several G-rich Sp-1 transcription factor binding motifs in tandem.
This finding correlates well with the finding that TATA-less promoters have multiple start sites compared to promoters containing a TATA-box motif but still give rise to a single protein (Suzuki et al., 2001).
Although many genes have multiple promoters, little attention has been focused on how these relate to one another; nor has much study been directed at relationships between promoters of adjacent genes.
Most human genes have multiple promoters and each promoter has multiple TSSs (Frith et al., 2008; Sandelin et al., 2007).
In addition, the use of alternative promoters depends on the promoter type: conserved tissue-specific promoters have a better defined TSS and are TATA-enriched, while more loosely defined CpG-rich promoters have a broader promoter region, often with multiple alternative promoters and many TSSs (Carninci et al., 2006).
