Control elements transcription

Table 37-3. Some of the transcription control elements, their consensus sequences, and the factors that bind to them which are found in mammalian genes transcribed by RNA polymerase II. A complete list would include dozens of examples. The asterisks mean that there are several members of this family.

In eukaryotes, the tRNA genes exist as multiple copies and are transcribed by RNA polymerase III (RNA Pol III). As in prokaryotes, several tRNAs may be transcribed together to yield a single pre-tRNA molecule that is then processed to release the mature tRNAs. The promoters of eukaryotic tRNA genes are unusual in that the transcriptional control elements are located downstream (i.e. on the 3 side) of the transcriptional start site (at position +1). In fact they lie within the gene itself. Two such elements have been identified, called the A box and B box (Fig. 3). Transcription of the tRNA genes by RNA Pol III requires transcription factor IIIC (TFIIIC) as well as TFIIIB. THIIC binds to the A and B boxes whilst TFIIIB binds upstream of the A box. TFIIIB contains three subunits, one of which is TBP (TATA binding protein), the polypeptide required by all three eukaryotic RNA polymerases. 

For example, alternative transcription-control elements regulate expression of the mammalian gene that encodes transthyretin (TTR), which transports thyroid hormone in blood and the cerebrospinal fluid that surrounds the brain... 

In eukaryotic genomes, DNA transcription control elements may be located many kilobases away from the promoter they regulate. Different control regions can control transcription of the same gene in different cell types. 

Most Eukaryotic Genes Are Regulated by Multiple Transcription-Control Elements... 

The various transcription-control elements found in eukaryotic DNA are binding sites for regulatory proteins. In this section, we discuss the identification, purification, and structures of these transcription factors, which function to activate or repress expression of eukaryotic protein-coding genes. 

GAL4 protein binds to UAS al sequences. When a copy of UASgal was cloned upstream of a TATA box followed by a lacZ reporter gene, expression of lacZ was activated in galactose media in wild-type cells, but not in gal4 mutants. These results showed that UAS al is a transcription-control element activated by the GAL4 protein in galactose media. 

Chromosomal localization will be augmented (e.g., by the rep gene, which allows targeting to chromosome 19) and gene expression regulated by specific transcriptional control elements (6). (Reproduced with permission from Pergamon Press.)... 

Robertson, L.M. et al., Regulation of c-fos expression in transgenic mice requires multiple interdependent transcription control elements, Neuron 14, 241, 1995. 

Zick A, Onn I, Bezalel R et al. Assigning functions to genes Identification of S-phase expressed genes in Leishmania major based on post-transcriptional control elements. Nucleic Acids Res 2005 33(13) 4235-42. 

Given the overlap in transcriptional control elements between MHC class I and class II expression, it is possible that the defect in IFN-y-stimulated MHC class II expression may extend to IFN-y-stimulated MHC class I expression. MHC class I and class II promoters share analogous S-X-Y motifs (Ting and Baldwin 1993 VAN DEN Elsen et al. 1998). Moreover, CIITA and IRF-1 are IFN-y-induced transcription factors that are critical for class 1 and class II transcription (Boss 1997 Muhlethaler-Mottet et al. 1998). 

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