High impact information on LOC396498

• This "delta 1-crystallin enhancer" activates transcription from the delta 1-crystallin promoter 20- to 40-fold in lens cells and to various degrees with other promoters [1].
• Overexpression of delta EF2a/cSOX-2 increased delta 1-crystallin enhancer activity to a plateau in lens cells, but not in fibroblasts, consistent with the previously drawn conclusion that delta EF2a activates transcription only in concert with another factor present in the lens [2].
• We have studied the mechanism of delta 1-crystallin gene activation, which occurs early in lens cell differentiation, and have previously shown that an essential element of the delta 1-crystallin enhancer is bound by a group of nuclear factors, delta EF2, among which delta EF2a is highly enriched in lens cells [2].
• The lens-specific expression of the delta 1-crystallin gene is governed by an enhancer in the third intron, which binds a positive (delta EF2) and negative (delta EF1) factor in its core region [3].
• Insulin-like growth factor I (IGF-I) and insulin regulate expression of the endogenous delta 1-crystallin gene in embryonic lens cells that express receptors for both peptides [4].

Biological context of LOC396498

• The complete sequence of the chicken delta 1 crystallin gene and its 5' flanking region [5].
• In Southern blots of human genomic DNA, chicken delta 1-crystallin cDNA hybridized only to the human ASL gene; moreover, the two chicken delta-crystallin genes accounted for all the sequences in the chicken genome able to cross-hybridize with a human ASL cDNA, with preferential hybridization to the delta 2 gene [6].
• Lens-preferred activity of chicken delta 1- and delta 2-crystallin enhancers in transgenic mice and evidence for retinoic acid-responsive regulation of the delta 1-crystallin gene [7].
• To further analyze the transcriptional component of this hormonal effect, transient transfections of lens cells were prepared with DNA constructs containing deletions of the delta 1-crystallin promoter and the chloramphenicol acetyltransferase reporter gene [4].
• In previous work we have shown that most HpaII sites become hypomethylated within the delta 1-crystallin gene long after delta-crystallin gene activation [8].

Anatomical context of LOC396498

• A comparison of lens epithelium and fibers established that levels of delta 2-crystallin RNA are the same but those of delta 1-crystallin RNA are over 100-fold higher in fibers compared to epithelial cells [9].
• Competition experiments with purified fragments from the delta 1-crystallin gene promoter showed that binding of transcription factor(s) from the HeLa cell extract to this G+C-rich region is required for promoter activity in vitro [10].
• However, when the ES cells were injected into a blastocyst and allowed to differentiate into various somatic cells of an embryo, CAT expression was observed exclusively in lens, and the expression was dependent upon the delta 1-crystallin enhancer [11].

Associations of LOC396498 with chemical compounds

• Published evidence indicates that the chick delta 1 crystallin gene encodes the major structural protein of embryonic lens fibres, whereas the closely related delta 2 gene may encode the urea-cycle enzyme argininosuccinate lyase (ASL) [12].
• These data confirm the roles of histidine in the catalytic process of this enzyme-crystallin and suggest that the change of His91 to Gln91 observed in the duck and chicken delta 1-crystallin molecules may be sufficient to account for the lack of enzymatic activity of those proteins [13].
• His91, His110, His162 and His178, were converted to asparagine residues in an effort to define the role of histidines in the catalytic process of this enzyme-crystallin and to explain the lack of enzyme activity in the delta 1-crystallin protein [13].

Other interactions of LOC396498

• This accumulation of delta-crystallin RNA during lens induction operates selectively on the delta 1-crystallin transcripts whereas delta 2-crystallin/argininsosuccinate lyase RNA is detectable at lower levels in all developing ocular tissues throughout this period [14].
• A nuclear factor delta EF1, which binds to the essential element of the delta 1-crystallin enhancer core, was molecularly cloned from the chicken by a southwestern method [15].
• A 77-nucleotide DNA segment of the delta 1-crystallin promoter from nucleotide positions-120 to -43 confers sensitivity to insulin and IGF-I [4].

Analytical, diagnostic and therapeutic context of LOC396498

• We previously reviewed what we had learned about the regulation of the delta 1-crystallin gene through experiments using gene transfer techniques [Kondoh et al. (1986) Cell Differ. 19, 151-160] [16].

References