Human monoclonal antibodies to HIV-1 gp140 from mice bearing YAC-based human immunoglobulin transloci.

Mice carrying human immunoglobulin transloci were immunised with HIV-1 gp140 antigen to gain insight into the range and nature of human monoclonal antibodies (mAbs) that can be elicited from such humanised mice. Using five-feature mice that harbour YAC-based germline-configuration human IgM, Igκ and Igλ transloci in a mouse background disrupted for endogenous mouse IgH and Igκ expression, gp140-specific human IgM mAbs were readily elicited following serial immunisation. These mAbs were converted to human IgG1 format and were found to bind diverse epitopes within gp140, exhibiting high functional affinity for the antigen-typically in the nanomolar or sub-nanomolar range.

HS5 of the human beta-globin locus control region: a developmental stage-specific border in erythroid cells.

Elements with insulator/border activity have been characterized most extensively in Drosophila melanogaster. In vertebrates, the first example of such an element was provided by a hypersensitive site of the chicken beta-globin locus, cHS4. It has been proposed that the homologous site in humans, HS5, functions as a border of the human beta-globin locus.

Intergenic transcription and developmental remodeling of chromatin subdomains in the human beta-globin locus.

Gene activation requires chromatin remodeling complexes, which hyperacetylate histones and enable factor access; however, the targeting mechanisms leading to the establishment and maintenance of large, hyperacetylated DNase-sensitive chromatin domains are unknown. Recent work has shown that histone acetyltransferases are associated with RNA-pol II complexes, suggesting that transcription of chromatin plays a role in chromatin modification. Here we show the human beta-globin locus is divided into three differentially activated chromatin subdomains.

Transcriptional activation by hypersensitive site three of the human beta-globin locus control region in murine erythroleukemia cells.

In this paper we describe a complete deletional analysis of hypersensitive site three (HS3) of the human beta-globin Locus Control Region (LCR). The previously defined core fragment consists of 6 footprinted regions, with multiple binding sites for the erythroid-specific factor GATA-1 and G-rich motifs that can interact with ubiquitous factors such as Sp1 and TEF-2. We show in this paper that the 5' half of this fragment is the most important for activity in murine erythroleukemia (MEL) cells.

The chicken beta/epsilon-globin enhancer directs autonomously regulated, high-level expression of the chicken epsilon-globin gene in transgenic mice.

In transiently transfected chicken erythroid cells, beta-like globin gene switching is mediated through differential activation of the cis-linked embryonic epsilon- and adult beta-globin genes by a shared enhancer. Two underlying mechanisms have been proposed: (i) tissue- and stage-specific factors activate the beta-globin promoter in adult erythroid cells (autonomous regulation); and (ii) the epsilon-globin promoter, although transcriptionally competent in both embryonic and adult cells, is suppressed at the adult stage through competition with the beta-globin promoter for interaction with the enhancer (competitive regulation). Analyses of transgenic mice carrying the chicken beta/epsilon-globin locus demonstrated that both genes depended on the enhancer for erythroid expression, but only the epsilon-globin gene exhibited developmentally appropriate transcription at levels comparable to the endogenous mouse globin genes.