To resolve the apparent paradox of hypermethylated LTRs possessing transcriptional activities, we studied the ERV-9 LTR retrotransposon located at the 5' border of the transcriptionally active β-globin gene locus in human erythroid progenitor and erythroleukemia K562 cells.
Using chromatin immunoprecipitation assays, we show that PIAS3 preferentially occupies the β-globin promoter in undifferentiated murine erythroleukemia cells.
Transient reporter-gene experiments in MEL and human erythroleukaemia K-562 cells with recombinant constructs containing B1-559 fragments linked to HS-2 (hypersensitive site-2) sequences of human β-globin gene LCR (locus control region) indicated potential cooperation upon erythropoiesis and globin gene expression.
These recombinant virions were used to infect a human erythroleukemia cell line which normally does not express the beta-globin gene (K562), or a human nasopharyngeal carcinoma cell line (KB).
Both proteins were expressed in and secreted by murine erythroleukemia cells under the control of the human beta-globin promoter placed down-stream from the human globin locus control region.
A cosmid construct containing extensive human gamma- and beta-globin gene promoter and structural sequences as well as upstream control sequences also exhibits higher levels of globin gene transcription in K562 NE than in HeLa NE.
Activation of the beta-globin promoter by the locus control region correlates with binding of a novel factor to the CAAT box in murine erythroleukemia cells but not in K562 cells.
Controls with the beta-globin gene, which is constitutively nonexpressed in Namalva-S cells but upon induction is highly expressed in murine erythroleukemia cells, completely confirmed the conclusion we had made for the intranuclear localization of c-myc.
Human fetal erythroid x murine erythroleukemia cell hybrids undergo human fetal (gamma) to adult (beta) globin gene switching in vitro under the control of a mechanism located on human chromosome 11.
Expression from a virally transferred gamma- or beta-globin gene exceeded endogenous gamma- or beta-globin expression by a factor of 6 or more in the human erythroleukemia line KMOE, in which the endogenous globin genes are weakly inducible.
We constructed retroviral vectors with a human beta-globin gene and the determinant for a single hypersensitive site and measured beta-globin gene expression after retroviral infection of murine erythroleukemia cells.
To determine the critical cis-acting elements, hybrid genes containing elements of the gamma and beta globin genes were transfected into K562 cells, a human erythroleukemia line.
Introduction of a virus containing the beta-globin gene with introns into murine erythroleukemia cells resulted in inducible expression of human beta-globin RNA and protein, while the viruses containing the minigene were inactive.
In addition, beta-globin gene expression has been evaluated in human erythroleukemia cells, K562 cells, and, although stable transformants with integrated beta-globin genes have been obtained, none of these transformants expressed the added beta-globin genes.
A 3.7-kilobase (kb) genomic clone of the human beta-globin gene, including 1.5-kb upstream and approximately 0.5-kb downstream, was utilized in chromosomal in situ hybridization for precise mapping of the beta-globin locus on peripheral blood lymphocyte-derived metaphases from a normal male, and for further evaluation of a clonal t(7;11) (q22;p15) translocation on bone marrow-derived metaphases from a 46-year-old male with erythroleukemia.