Utilization of the second polyadenylation signal at the 3' end of the chicken carbonic anhydrase II gene

A novel carbonic anhydrase II mRNA isolated from mature chicken testis displays a TATA box and other promoter sequences in a leader 5' untranslated region not present in somatic tissues

The primary structure of a novel carbonic anhydrase II-encoding cDNA clone (CAII) isolated from a chicken testis cDNA library is presented. The size of the CAII mRNA obtained from meiotic and haploid chicken testis cells is larger than the corresponding mRNA from immature testis and somatic tissues. The nucleotide sequence of the chicken testis CAII clone revealed a protein-coding region identical to the published sequence of CAII mRNA from erythroid cells. However, the 5' untranslated region (UTR) of the testis CAII mRNA is larger than the corresponding somatic sequence. The 5' UTR contains a leader sequence not present in the CAII mRNA isolated from erythroid cells or chick retina. The additional 5' UTR of the mRNA displays a TATA box, located 23-30 bp upstream from the cap site of the CAII mRNA transcribed in erythroid cells, and several G+C-rich boxes. Our results suggest that the use of a testis-specific promoter would result in the incorporation of somatic promoter sequences into the 5' UTR of the testis message.

High levels of aldehyde dehydrogenase transcripts in the undifferentiated chick retina

A cDNA clone corresponding to chicken aldehyde dehydrogenase (ALDH) mRNA was isolated from a library representing the polyadenylated RNAs expressed in the retina of day 3.5 chick embryos. The profile of ALDH RNA expression was examined in different tissues as well as at different stages of development in the chick embryo. A notable feature of this analysis was the high level of ALDH transcripts found in the undifferentiated cells of the retina. A 20-fold decrease in ALDH RNA levels was observed upon retinal differentiation, in contrast to the kidney, liver and gut where tissue maturation was accompanied by an increase in ALDH mRNA levels. The observations reported here suggest an important role for the ALDH enzyme in retinal development. One possibility is that retinal, the aldehyde form of vitamin A, serves as a substrate for ALDH in the developing retina, resulting in the formation of retinoic acid which has been implicated in various differentiation processes.