Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effects of thyroid hormone (T3) on nuclear protein-DNA interactions by using dimethyl sulfate (DMS) and DNase I ligation-mediated PCR footprinting. We examined an endogenous gene the growth hormone (GH) gene, and a stably transfected plasmid containing the chicken lysozyme silencer (F2) T3 response element (TRE) gene, F2-TRE-TK-CAT, both in pituitary tumor (GC) cells. The 235-1 cell line, which expresses prolactin (PRL) and Pit-1, but not the T3 receptor (TR) or GH, was used as a control. DMS and DNase I footprinting identified protected G residues in the Pit-1, Sp1, and Zn-15 binding sites of the GH gene in GC, but not in 235-1, cells. There was no specific protection of the tripartite GH TRE at -180 bp against either DMS or DNase I in the absence or presence of T3 in either cell line. However, T3 increased protection of the Pit-1 and Sp1 binding sites against DMS in GC cells. In GC cells stably transfected with a plasmid containing F2-TRE-TK-CAT or TRalpha, chloramphenicol acetyltransferase expression was T3 inducible and DMS footprinting revealed both F2 TRE TR-binding half sites in a pattern suggesting the binding of TR homodimers before and during T3 exposure. We conclude that the GH gene is accessible to specific nuclear proteins in GC, but not in 235-1, cells and that T3 enhances this interaction, although there is no evidence of TR binding to the low-affinity rat GH TRE. The presence of TR binding to the high-affinity F2 TRE before and during T3 exposure suggests that reversible interaction of T3 with DNA-bound TRs, rather than transient T3-TR contact with TREs, determines the level of T3-stimulated transcriptional activation.
 ...
PMID:In vivo genomic footprinting of thyroid hormone-responsive genes in pituitary tumor cell lines. 875 47

Here, we describe the cloning and further characterization of chicken ARBP, an abundant nuclear protein with a high affinity for MAR/SARs. Surprisingly, ARBP was found to be homologous to the rat protein MeCP2, previously identified as a methyl-CpG-binding protein. A region spanning 125 amino acids in the N-terminal halves is 96.8% identical between chicken ARBP and rat MeCP2. A deletion mutation analysis using Southwestern and band shift assays identified this highly conserved region as the MAR DNA binding domain. Alignment of chicken ARBP with rat and human MeCP2 proteins revealed six trinucleotide amplifications generating up to 34-fold repetitions of a single amino acid. Because MeCP2 was previously localized to pericentromeric heterochromatin in mouse chromosomes, we analyzed the in vitro binding of ARBP to various repetitive sequences. In band shift experiments, ARBP binds to two chicken repetitive sequences as well as to mouse satellite DNA with high affinity similar to that of its binding to chicken lysozyme MAR fragments. In mouse satellite DNA, use of several footprinting techniques characterized two high-affinity binding sites, whose sequences are related to the ARBP binding site consensus in the chicken lysozyme MAR (5'-GGTGT-3'). Band shift experiments indicated that methylation increased in vitro binding of ARBP to mouse satellite DNA two- to fivefold. Our results suggest that ARBP/MeCP2 is a multifunctional protein with roles in loop domain organization of chromatin, the structure of pericentromeric heterochromatin, and DNA methylation.
 ...
PMID:Chicken MAR-binding protein ARBP is homologous to rat methyl-CpG-binding protein MeCP2. 927 41


<< Previous 1 2