The overlap of Inr and TATA elements sets the use of alternative transcriptional start sites in the mouse galectin-1 gene promoter

Chorioamnionitis and increased galectin-1 expression in PPROM --an anti-inflammatory response in the fetal membranes?

PROBLEM

Galectin-1 can regulate immune responses upon infection and inflammation. We determined galectin-1 expression in the chorioamniotic membranes and its changes during histological chorioamnionitis.

METHOD OF STUDY

Chorioamniotic membranes were obtained from women with normal pregnancy (n = 5) and from patients with pre-term pre-labor rupture of the membranes (PPROM) with (n = 8) and without histological chorioamnionitis (n = 8). Galectin-1 mRNA and protein were localized by in situ hybridization and immunohistochemistry. Galectin-1 mRNA expression was also determined by quantitative reverse transcriptase polymerase chain reaction.

RESULTS

Galectin-1 mRNA and protein were detected in the amniotic epithelium, chorioamniotic fibroblasts/myofibroblasts and macrophages, chorionic trophoblasts, and decidual stromal cells. In patients with PPROM, galectin-1 mRNA expression in the fetal membranes was higher (2.07-fold, P = 0.002) in those with chorioamnionitis than in those without. Moreover, chorioamionitis was associated with a strong galectin-1 immunostaining in amniotic epithelium, chorioamniotic mesodermal cells, and apoptotic bodies.

CONCLUSION

Chorioamnionitis is associated with an increased galectin-1 mRNA expression and strong immunoreactivity of the chorioamniotic membranes; thus, galectin-1 may be involved in the regulation of the inflammatory responses to chorioamniotic infection.

Emergence of hormonal and redox regulation of galectin-1 in placental mammals: implication in maternal-fetal immune tolerance

Galectin-1 is an anti-inflammatory lectin with pleiotropic regulatory functions at the crossroads of innate and adaptive immunity. It is expressed in immune privileged sites and is implicated in establishing maternal-fetal immune tolerance, which is essential for successful pregnancy in eutherian mammals. Here, we show conserved placental localization of galectin-1 in primates and its predominant expression in maternal decidua. Phylogenetic footprinting and shadowing unveil conserved cis motifs, including an estrogen responsive element in the 5' promoter of LGALS1, that were gained during the emergence of placental mammals and could account for sex steroid regulation of LGALS1 expression, thus providing additional evidence for the role of galectin-1 in immune-endocrine cross-talk. Maximum parsimony and maximum likelihood analyses of 27 publicly available vertebrate and seven newly sequenced primate LGALS1 coding sequences reveal that intense purifying selection has been acting on residues in the carbohydrate recognition domain and dimerization interface that are involved in immune functions. Parsimony- and codon model-based phylogenetic analysis of coding sequences show that amino acid replacements occurred in early mammalian evolution on key residues, including gain of cysteines, which regulate immune functions by redox status-mediated conformational changes that disable sugar binding and dimerization, and that the acquired immunoregulatory functions of galectin-1 then became highly conserved in eutherian lineages, suggesting the emergence of hormonal and redox regulation of galectin-1 in placental mammals may be implicated in maternal-fetal immune tolerance.

Structural organization and functional properties of miniature DNA insertion sequences in yersiniae

YPALs (Yersinia palindromic sequences) are miniature DNA insertions scattered along the chromosomes of yersiniae. The spread of these intergenic repeats likely occurred via transposition, as suggested by the presence of target site duplications at their termini and the identification of syntenic chromosomal regions which differ in the presence/absence of YPAL DNA among Yersinia strains. YPALs tend to be inserted closely downstream from the stop codon of flanking genes, and many YPAL targets overlap rho-independent transcriptional terminator-like sequences. This peculiar pattern of insertion supports the hypothesis that most of these repeats are cotranscribed with upstream sequences into mRNAs. YPAL RNAs fold into stable hairpins which may modulate mRNA decay. Accordingly, we found that YPAL-positive transcripts accumulate in Yersinia enterocolitica cells at significantly higher levels than homologous transcripts lacking YPAL sequences in their 3' untranslated region.

Galectin genes: regulation of expression

In this review we have summarized the more recent studies on the expression of mammalian galectins. One interesting observation that can be made is that in most of microarrays and/or differential display analysis performed in recent years one or more galectins have been picked up. From a critical evaluation of the pertinent studies the main conclusion that can be drawn is that, although it is not yet clear whether the 14 galectins identified so far have functions in common, a striking common feature of all galectins is the strong modulation of their expression during development, differentiation stages and under different physiological or pathological conditions. This suggests that the expression of different galectins is finely tuned and possibly coordinated. In spite of these observations it is rather unexpected that very few studies have been performed on the molecular mechanisms governing the activity of galectin genes.

Two Inr elements are important for mediating the activity of the proximal promoter of the human gonadotropin-releasing hormone receptor gene

Differential usage of several transcription start sites in the human GnRH receptor gene was evident in human brain and pituitary. To locate the promoter responsible for a cluster of the 3' CAP sites from -635 to -578 (relative to ATG) found in the pituitary, a proximal promoter element was identified at -677/-558 by 5' and 3' deletion mutant analysis. The promoter element drove a 13.1 +/- 0.6-fold increase in reporter gene activity in an orientation-dependent manner in the mouse gonadotrope-derived alphaT3-1 cells. Within the core promoter element, two functional AT-rich Inr motifs, interacting with the same protein factor with different affinities, were identified. By Southwestern blot analysis and competitive gel mobility shift assays, multiple nuclear factors (36-150 kDa) were found to interact specifically with the core promoter element. Interestingly, these nuclear proteins also interacted with a previously identified distal promoter of the human GnRH receptor gene. Taken together, our studies suggested that these two promoters share common protein factors to regulate transcription initiations at two different regions. Additional mechanisms are needed to modulate the efficiencies of individual promoters for developmental and/or tissue-specific regulations.

The abundant class of nemis repeats provides RNA substrates for ribonuclease III in Neisseriae

About 2% of the Neisseria meningitidis genome is made up by nemis, short DNA sequences which feature long terminal inverted repeats (TIRs). Most nemis are interspersed with single-copy DNA and are found at close distance from cellular genes. In this work, we demonstrate than RNAs spanning nemis of different length and sequence compositions are specifically cleaved at hairpins formed by nemis termini by total cellular lysates derived from both Escherichia coli and Neisseria lactamica strains. The use of cellular extracts from E. coli strains impaired in the activity of known ribonucleases let to establish that cleavage at nemis TIRs is specifically mediated by the endoribonuclease RNase III. Data set the base for the identification of all of the neisserial genes that are regulated by RNase III because of their physical association with nemis DNA.

Whole-genome organization and functional properties of miniature DNA insertion sequences conserved in pathogenic Neisseriae

The chromosome of pathogenic Neisseriae is peppered by members of an abundant family of small DNA sequences known as Correia elements. These DNA repeats, that we call nemis (for neisseria miniature insertion sequences) can be sorted into two major size classes. Both unit-length (154-158 bp) and internally rearranged (104-108 bp) elements feature long terminal inverted repeats (TIRs), and can potentially fold into robust stem-loop structures. Nemis are (or have been) mobile DNA sequences which generate a specific 2-bp target site duplication upon insertion, and strictly recall RUP, a repeated DNA element found in Streptococcus pneumoniae. The subfamilies of 26L/26R, 26L/27R, 27L/27R and 27L/26R elements, found by wide-genome computer surveys in both the Neisseria meningitidis and the Neisseria gonorrhoeae genomes, originate from the combination of TIRs which vary in length (26-27 bp) as in sequence content (L and R types). In both species, the predominant subfamily is made by the 26L/26R elements. The number of nemis is comparable in the N. meningitidis Z2491 (A serogroup) and the MC58 (B serogroup) strains, but is sharply reduced in the N. gonorrhoeae strain F1090. Consequently, several genes which are conserved in the two pathogens are flanked by nemis DNA in the meningococcus genome only. More than 2/3 of nemis are interspersed with single-copy DNA, and are found at close distance from cellular genes. Both primer extension and RNase protection data lend support to the notion that nemis are cotranscribed with cellular genes and subsequently processed, at either one or both TIRs, by a specific endoribonuclease, which plausibly corresponds to RNase III.