Graham H. Goodwin

Analysis of the HMGI nuclear proteins in mouse neoplastic cells induced by different procedures

Four malignant tumors induced in mouse by different experimental procedures were compared as regards their high-mobility-group (HMG) proteins. All tumors showed the complete set of three HMG proteins which we call HMGI-C, I-D, and I-E. The presence of the three HMGI proteins is a characteristic of the transformed phenotype regardless of whether the tumor was chemically, virally, or spontaneously derived. However, the level of expression of the HMGI proteins is not constant in the four tumors. Using reverse-phase HPLC, the individual HMGI proteins were isolated from the spontaneously derived tumor (Lewis lung carcinoma) and shown by amino acid analysis to be similar to those previously obtained from a tumor grown in nude mice by inoculation of in vitro-transformed cells.

The homeodomain protein PRH influences the differentiation of haematopoietic cells

Haematopoiesis involves the differentiation of a self-renewing stem cell into all of the lineages found in circulating blood. Myb-Ets transformed chicken blastoderm cells (MEPs) have many of the characteristics of multipotent haematopoietic cells and represent a useful model system for the study of haematopoiesis. The proline-rich homeodomain protein (PRH) has previously been shown to be expressed in the haematopoietic compartment. In this report we show that PRH mRNA and protein levels are down regulated as MEPs differentiate along the myelomonocytic and erythrocytic lineages. In contrast, PRH mRNA and protein levels remain high as MEPs differentiate toward the thrombocytic lineage. Over-expression of full length PRH in MEPs inhibits their transformation and/or proliferation. However, the over-expression of N-terminally truncated PRH proteins results in normally proliferating cells that are predominantly differentiated along the myelomonocytic and eosinophilic lineages. These results suggest that PRH plays a role in the proliferation and differentiation of haematopoietic cells.

Isolation and characterization of the gene coding for murine high-mobility-group protein HMGI-C

The HMGI-C protein is a nuclear factor expressed in human and rodent neoplastic cells which has been shown to be involved in the process of cell transformation. We have previously isolated the cDNA encoding murine HMGI-C and now we report the cloning and analysis of the mouse Hmgi-c gene. The gene is at least 50 kb long, contains five exons, and each of the three DNA-binding domains is encoded by a different exon. The location of exon-intron junctions was determined and shown to follow the GT-AG rule. The sequence revealed that the overall organization is similar to the gene encoding human HMGI(Y), the other member of the HMGI family, suggesting that HMGI genes probably evolved through gene duplication and exon shuffling events from an ancestral gene. A highly homologous pseudogene is also present in the mouse genome. Our results on Hmgi-c structure provide basic information to carry out further studies on the regulation of its expression.

Crystal structure of the proximal BAH domain of the polybromo protein

The BAH domain (bromo-associated homology domain) was first identified from a repeated motif found in the nuclear protein polybromo--a large (187 kDa) modular protein comprising six bromodomains, two BAH domains and an HMG box. To date, the BAH domain has no ascribed function, although it is found in a wide range of proteins that contain additional domains involved in either transcriptional regulation (e.g. SET, PHD and bromodomain) and/or DNA binding (HMG box and AT hook). The molecular function of polybromo itself also remains unclear, but it has been identified as a key component of an SWI/SNF (switching/sucrose non-fermenting)-related, ATP-dependent chromatin-remodelling complex PBAF (polybromo, BRG1-associated factors; also known as SWI/SNF-B or SWI/SNFbeta). We present in this paper the crystal structure of the proximal BAH domain from chicken polybromo (BAH1), at a resolution of 1.6 A (1 A=0.1 nm). Structure-based sequence analysis reveals several features that may be involved in mediating protein-protein interactions.

A homology‐based molecular model of the proline‐rich homeodomain protein Prh, from haematopoietic cells

A molecular structural model for the homeodomain of the haematopoietic protein Prh together with its DNA recognition sequence, has been built using the known crystal structure of the MATα2 homeodomain as a starting‐point. The modelling procedure used main and side‐chain optimisations by means of molecular mechanics/simulated annealing procedures to obtain stereochemically plausible geometries. The resulting structure has a number of specific interactions in both major and minor grooves of the DNA that serve to define the consensus binding sequence for Prh. In particular, the side‐chain of glutamine 50 is postulated to be involved in hydrogen bonds to adjacent adenine and cytosine bases within the consensus sequence.