High resolution physical mapping and identification of transcribed sequences in the Down syndrome region-2.

The identification and mapping of genes within the Down syndrome region is an important step toward a complete understanding of the pathogenesis of this disorder. The objective of the present work is to identify and map genes within the Down syndrome region-2. Chromosome 21 cosmid clones corresponding to "cosmid pockets" 121-124 have been first used as a starting material for generation of a single high resolution integrated cosmid/PAC contig with full EcoRI/SmaI restriction map. The integrated contig has been further anchored to genetic and physical maps through the positioning of 6 markers in the following order: ACTL5-D21S3-684G2T7-D21S71-D21S343-D21S 268. The entire contig covers 342 kb of the Down syndrome region-2 of chromosome 21. Subsequently, we have isolated, identified, and mapped four novel cDNAs which we have named N143, N144, CHD/333, and 90/3H1 and a potentially transcribed genomic sequence (E05133T7). Additionally, we have accurately located a previously described gene, the WRB gene, between the markers ACTL5-D21S268 within this Down Syndrome Region-2.

Conserved elements in the 5' regulatory region of the amyloid precursor protein gene in primates.

Oligonucleotides corresponding to conserved sites between the human and mouse amyloid precursor protein (APP) genes have been used to polymerase chain reaction (PCR) amplify and sequence the promoter region of the APP gene from chimpanzee, gorilla, orang-utan, papio and African green monkey. Several novel conserved potentially-regulatory sequences of the APP gene have been detected after alignment of the APP promoter sequences: an apolipoprotein E-B1 (APOE-B1) element at position -450, also present in the APOE gene, two activator protein-2 (AP-2) sites at positions -450 and -301 and an intermediate early-1 gene (IE1) site at position -280. These elements are conserved in all mammalian APP promoter sequences studied. Additionally a previously detected heat shock element (HSE) at position -317, and an activator protein-1 (AP-1) site at position -350 are also conserved. Knowledge of the essential regulatory elements at the APP gene constitute the basis for understanding its transcriptional control and subsequent model studies.

A novel silent variant at codon 711 and a variant at codon 708 of the APP sequence detected in Spanish Alzheimer and control cases.

Pathogenic mutations have been identified in exons 16 and 17 of the beta-amyloid precursor protein (APP) gene in some cases of early onset Alzheimer's disease. Screening of these exons in a number of familial and sporadic cases of Alzheimer's disease in Spain, resulted in the identification of a novel silent variant at codon 711 whose relevance to the AD pathogenesis remains unclear. The 708 variant was also detected in one of normal controls.

Positive and negative regulatory elements in the dnaA-dnaN-recF operon of Escherichia coli.

The recF gene of E coli lies within a cluster of genes which play essential roles in DNA replication; the gene order is dnaA dnaN recF gyrB. Each of these genes has its own promoters which, with the exception of dnaA promoters, reside entirely within the translated region of the respective preceding gene. In this report, we analyze the effect of the dnaA and dnaN promoters on recF expression by translational fusions between recF and the lacZ reporter gene. Our results indicate that recF is a distal gene of the dnaA operon, and support the previous proposal that dnaN and recF constitute a transcriptional unit under control of the dnaN promoters. They also suggest that dnaA, dnaN and recF are predominantly expressed from the same mRNA although transcriptional and/or post-transcriptional mechanisms should be specifically involved in lowering expression of the recF gene. Recently, we have localized 3 tandem transcription termination sites in the second half of the dnaN gene, downstream from the recF promoters. Neither of them shows the typical features of simple terminators and apparently they do not work in a minimal system of in vitro transcription. In this report, we present evidence that only one of them is dependent on the Rho protein. Although the operon structure allows coordinate expression of dnaA, dnaN and recF, the presence of internal promoters (the dnaN and recF promoters), which appear to be inducible by DNA damage, and intracistronic terminators, whose activity is inversely proportional to the efficiency of translation, permits expression of individual genes to be independently regulated in response to altered growth conditions.