Differential regulation of the two mRNA species of the rodent negative acute phase protein alpha 1-inhibitor 3

Caloric restriction promotes functional changes involving short-chain fatty acid biosynthesis in the rat gut microbiota

Caloric restriction (CR) is known to promote health and longevity, likely via modification of the gut microbiota (GM). However, functional and metabolic changes induced in the GM during CR are still unidentified. Here, we investigated the short- and long-term effects of CR on the rat GM using a metaproteogenomic approach. We show that a switch from ad libitum (AL) low fat diet to CR in young rats is able to induce rapid and deep changes in their GM metaproteomic profile, related to a reduction of the Firmicutes/Bacteroidetes ratio and an expansion of lactobacilli. Specifically, we observed a significant change in the expression of the microbial enzymes responsible for short-chain fatty acid biosynthesis, with CR boosting propionogenesis and limiting butyrogenesis and acetogenesis. Furthermore, these CR-induced effects were maintained up to adulthood and started to be reversed after a short-term diet change. We also found that CR alters the abundance of an array of host proteins released in stool, mainly related to epithelial barrier integrity and inflammation. Hence, our results provide thorough information about CR-induced modifications to GM and host functional activity, and might constitute the basis for novel GM-based approaches aimed at monitoring the effectiveness of dietary interventions.

A high affinity binding site for the polypyrimidine tract binding protein (PTB) is located in the 5'-untranslated region of the rat proteinase alpha1-inhibitor 3 variant I gene

As a first step towards understanding the mechanism underlying the differential gene expression of the two variants of the rat proteinase-inhibitor alpha1-inhibitor 3 (alpha1-I3) corresponding genomic clones were isolated. The 100% similarity between the sequence of one genomic clone and that of the alpha1-13 variant I cDNA strongly suggested that its 5'-sequence represented the upstream region of the corresponding gene. Several putative cis-regulatory elements were identified as well as a polypyrimidine tract located between the transcription start site of the alpha1-I3 variant I mRNA and the AUG codon. The polypyrimidine tract functions as a positive cis-element in a heterologous promoter. By electrophoretic mobility shift assays (EMSA) we have shown that a GST (glutathione S-transferase) fusion of the rat polypyrimidine tract binding protein (PTB) has a high affinity for the pyrimidine-rich sense strand but not for the complementary sequence of the 5'-untranslated region of the alpha1-I3 variant I gene.

The fatty acid synthase (FAS) gene and its promoter in Rattus norvegicus

Screening of rat liver genomic libraries yielded 5 overlapping clones for rat fatty acid synthase (FAS). From these clones we determined the 18,170 bp sequence of the rat FAS together with 5,028 bp of the 5'-flanking region and 515 bp of the 3'-adjacent genomic sequence. The two FAS transcripts which differ only in the positions of their polyadenylation/termination sites consist of one untranslated and 42 translated exons. Surprisingly, the substrate binding site for enoyl reductase, one of the FAS component functions, is interrupted by an intron. The sizes and the boundaries of the individual domains could be mapped in relation to the exon/intron structure of the gene. These eight partial functions coincide with discrete units of exons. The acyl carrier protein with its prosthetic 4'-phosphopantetheine group is located within a single exon supporting the idea that rat FAS has evolved by gene fusion. Using primer extension the main transcription start site of the FAS mRNA in both hepatic and mammary gland tissues was located at 5,028 bp in the sequence determined. As expected of a gene which is pretranslationally regulated the 5'-flanking region contains, in addition to TATA and CAAT boxes, consensus sequences for several DNA binding proteins.