Enhancement of hydroxyindole-O-methyltransferase and DNA-dependent RNA polymerase activities induced by oestradiol in rat pineals in culture. (41/43)

1. Hydroxyindole-O-methyltransferase and DNA-dependent RNA polymerase activities were determined in the pineal gland removed from the ovariectomised rat and cultured under various experimental conditions. 2. The transferase activity declined very slowly during 24 h of incubation. 17beta-Oestradiol significantly increased the transferase activity within 2h after the addition, and the extent of increase was dose-dependent within the concentration range from 0.1 to 15 nM, being increased by 80% at 15 nM. Enhancement of the transferase activity by oestradiol was abolished not only by inhibitors of protein synthesis (cycloheximide and puromycin), but also by those of RNA synthesis (actinomycin D and alpha-amanitin). It was also blocked by clomiphene citrate, an agent which is known to inhibit the binding of steroid hormones to their respective receptors. 3. RNA polymerase activity (forms A and B) declined rapidly during the initial period of pineal culture. Oestradiol (15 nM) increased the RNA polymerase B activity by 50% within 2 h after the addition. The increase was dose-dependent within the concentration range from 0.1 to 15 nM, and was abolished by clomiphene citrate. 4. The possibility is suggested that the pineal is a target organ of oestradiol, and that the steroid-induced reaction sequence in the pineal conforms to that is known in other target organs.  (+info)

Gene duplications as a recurrent theme in the evolution of the human pseudoautosomal region 1: isolation of the gene ASMTL. (42/43)

We have isolated a novel gene, ASMTL (acetylserotonin methytransferase-like ), in the pseudoautosomal region (PAR1) on the human sex chromosomes. ASMTL represents a unique fusion product of two different full-length genes of different evolutionary origin and function. One part is homologous to the bacterial maf/orfE genes. The other part shows significant homology to the entire open reading frame of the previously described pseudoautosomal gene ASMT, encoding the enzyme catalysing the last step in the synthesis of melatonin. We have also detected the identity of one exon (1A) of ASMT to exon 3 in yet another pseudoautosomal gene, XE7. The data presented suggest that exon duplication and exon shuffling as well as gene fusion may represent common characteristics in the pseudoautosomal region.  (+info)

Structural analysis of the chicken hydroxyindole-O-methyltransferase gene. (43/43)

Hydroxyindole-O-methyltransferase (HIOMT) catalyzes the final step of melatonin synthesis, a neurohormone involved in photoperiodism and produced specifically in the pineal gland and in the retina. In the chicken, HIOMT gene transcription appears to be controlled by a circadian oscillator located in the pineal gland. We have characterized the chicken HIOMT gene over 17 kb, including 2.9 kb of 5'-flanking sequence. The major transcript (1.6 kb) is composed of eight exons distributed over 7.5 kb of genomic DNA. A ninth alternative exon was identified 6 kb downstream of exon 8. It was found in minor transcripts in the pineal gland and in the retina. Sequence similarity between exons 8 and 9 suggests their origin by exon duplication. Due to early stop codons, inclusion of exon 9 truncates the open reading frame by up to 33%. A restriction fragment length polymorphism was detected for a BglII site in intron 8. Fluorescence hybridization localized the HIOMT gene on chicken chromosome 1q22. The 5'-flanking region contains GATTAA and TAATCC sequences that may be related to tissue-specific expression. An ATTTAAAT sequence at position -29 would play the role of a TATA box, as evidenced by electrophoretic mobility shift assay. Information obtained in this study open the way to further studies aimed at analyzing the circadian rhythm of transcription at promoter level.  (+info)