Transcription tissue specificity

Cummins, I. and Murphy, D.J. (1992) cDNA sequence of a sunflower oleosin and transcript tissue specificity. Plant Mol. Biol. 19, 873-876. 

A most important function of vitamin A is in the control of cell differentiation and mrnover. PsA-trans-retinoic acid and 9-cw-retinoic acid (Figure 45-1) regulate growth, development, and tissue differentiation they have different actions in different tissues. Like the steroid hormones and vitamin D, retinoic acid binds to nuclear receptors that bind to response elements of DNA and regulate the transcription of specific genes. There are two families of nuclear retinoid receptors the retinoic acid receptors (RARs) bind all-rrijw-retinoic acid or 9-c -retinoic acid, and the retinoid X receptors (RXRs) bind 9-cw-retinoic acid. 

IA (1997) Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors a and (3. Endocrinol. 138, 863-70. 

Northern blot analysis revealed that expression of NHE-1 is tissue-specific with highest transcript abundance in stomach and minimal levels in liver and skeletal muscle. Moreover, there is physiological evidence that certain segments of the nephron lack a basolateral Na /H" exchanger [76]. Using RT-PCR, Krapf and Solioz [77] observed that NHE-1 transcripts are not detectable in SI and S2 segments of superficial nephrons. 

In Drosophila the two tissue-specific mRNAs are generated by alternative splicing of a single primary transcript (Fig. 9). In vertebrates the two tissue specific AADC transcripts are generated from two alternative promoters (Fig. 11) (Albert et al., 1992 Ichinose et al., 1992 Thai et al., 1993). In neural tissue transcription initiates from exon Nl, whereas in non-neural tissue transcription initiates from exon LI. This produces two distinct primary transcripts that are then spliced from the first exon (LI or Nl) to exon 2 to generate two tissue-specific mRNAs. Translation initiates within exon 2, such that the same AADC protein product is synthesized from both AADC mRNAs. 

The highly restricted tissue-specific transcription of c-mos poses an interesting problem in gene regulation during germ cell development. Moreover, c-mos is transcribed from different promoters in mouse spermatocytes and oocytes (Fig. 4) (Propst et al., 1987). In spermatocytes, transcription initiates approximately 280 nucleotides upstream of the c-mos ATG (Propst et al., 1987), whereas the transcription start site in oocytes has been mapped to 53 base pairs upstream of the ATG (Pal et al., 1991). Neither the spermatocyte nor oocyte promoter regions are... 

Paules, R. S., Propst, F Dunn, K. J., Blair, D. G., Kaul, K., Palmer, A. E., and Vande Woude, G. F. (1988). Primate c-mos proto-oncogene structure and expression transcription initiation both upstream and within the gene in a tissue-specific manner. Oncogene 3 59-68. 

Schoonjans K, Peinado-Onsurbe J, Le-febvre AM, Heyman RA, Briggs M, Deeb S, et al. PPARalpha and PPARgam-ma activators direct a distinct tissue-specific transcriptional response via a PPRE... 

Ligand-bound corticosteroid receptors have been shown to interact to form heterodimers with other transcription factors, such as the jun protein. Such interactions are responsible for transactivation of the ds-regulatory sites known as AP-1 sites and for the glucocorticoid-mediated suppression of transcription, such as that seen in the pro-opiomelanocortin gene. A number of such specific protein interactions have been reported these interactions and their locations relative to other transcription factors transform a ubiquitous steroid hormone signal into a tissue-specific, graded cellular response. 

The fact that a receptor dimer identifies a HRE does not assure, by itself, the transcription of the gene. This is a necessary, but insufficient, condition. Once the dimer-HRE interaction has been produced, the machinery of transcription needs to be assembled, requiring the binding of other intermediary cofactors. Some of these are tissue specific, and others recognize only a particular receptor dimer, thus obviating others that could recognize the same HRE. 

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