The role of transcriptional activator GATA-1 at human β-globin HS2

GATA-1 is an erythroid activator that binds β-globin gene promoters and DNase I hypersensitive sites (HSs) of the β-globin locus control region (LCR). We investigated the direct role of GATA-1 interaction at the LCR HS2 enhancer by mutating its binding sites within minichromosomes in erythroid cells. Loss of GATA-1 in HS2 did not compromise interaction of NF-E2, a second activator that binds to HS2, nor was DNase I hypersensitivity at HS2 or the promoter of a linked ε-globin gene altered. Reduction of NF-E2 using RNAi confirmed the overall importance of this activator in establishing LCR HSs. However, recruitment of the histone acetyltransferase CBP and RNA pol II to HS2 was diminished by GATA-1 loss. Transcription of ε-globin was severely compromised with loss of RNA pol II from the transcription start site and reduction of H3 acetylation and H3K4 di- and tri-methylation in coding sequences. In contrast, widespread detection of H3K4 mono-methylation was unaffected by loss of GATA-1 in HS2. These results support the idea that GATA-1 interaction in HS2 has a prominent and direct role in co-activator and pol II recruitment conferring active histone tail modifications and transcription activation to a target gene but that it does not, by itself, play a major role in establishing DNase I hypersensitivity

Height and timing of growth spurt during puberty in young people living with vertically acquired HIV in Europe and Thailand.

OBJECTIVE: The aim of this study was to describe growth during puberty in young people with vertically acquired HIV. DESIGN: Pooled data from 12 paediatric HIV cohorts in Europe and Thailand. METHODS: One thousand and ninety-four children initiating a nonnucleoside reverse transcriptase inhibitor or boosted protease inhibitor based regimen aged 1-10 years were included. Super Imposition by Translation And Rotation (SITAR) models described growth from age 8 years using three parameters (average height, timing and shape of the growth spurt), dependent on age and height-for-age z-score (HAZ) (WHO references) at antiretroviral therapy (ART) initiation. Multivariate regression explored characteristics associated with these three parameters. RESULTS: At ART initiation, median age and HAZ was 6.4 [interquartile range (IQR): 2.8, 9.0] years and -1.2 (IQR: -2.3 to -0.2), respectively. Median follow-up was 9.1 (IQR: 6.9, 11.4) years. In girls, older age and lower HAZ at ART initiation were independently associated with a growth spurt which occurred 0.41 (95% confidence interval 0.20-0.62) years later in children starting ART age 6 to 10 years compared with 1 to 2 years and 1.50 (1.21-1.78) years later in those starting with HAZ less than -3 compared with HAZ at least -1. Later growth spurts in girls resulted in continued height growth into later adolescence. In boys starting ART with HAZ less than -1, growth spurts were later in children starting ART in the oldest age group, but for HAZ at least -1, there was no association with age. Girls and boys who initiated ART with HAZ at least -1 maintained a similar height to the WHO reference mean. CONCLUSION: Stunting at ART initiation was associated with later growth spurts in girls. Children with HAZ at least -1 at ART initiation grew in height at the level expected in HIV negative children of a comparable age

Friend of GATA (FOG) Interacts with the Nucleosome Remodeling and Deacetylase Complex (NuRD) to Support Primitive Erythropoiesis in Xenopus laevis

Friend of GATA (FOG) plays many diverse roles in adult and embryonic hematopoiesis, however the mechanisms by which it functions and the roles of potential interaction partners are not completely understood. Previous work has shown that overexpression of FOG in Xenopus laevis causes loss of blood suggesting that in contrast to its role in mammals, FOG might normally function to repress erythropoiesis in this species. Using loss-of-function analysis, we demonstrate that FOG is essential to support primitive red blood cell (RBC) development in Xenopus. Moreover, we show that it is specifically required to prevent excess apoptosis of circulating primitive RBCs and that in the absence of FOG, the pro-apoptotic gene Bim-1 is strongly upregulated. To identify domains of FOG that are essential for blood development and, conversely, to begin to understand the mechanism by which overexpressed FOG represses primitive erythropoiesis, we asked whether FOG mutants that are unable to interact with known co-factors retain their ability to rescue blood formation in FOG morphants and whether they repress erythropoiesis when overexpressed in wild type embryos. We find that interaction of FOG with the Nucleosome Remodeling and Deacetylase complex (NuRD), but not with C-terminal Binding Protein, is essential for normal primitive RBC development. In contrast, overexpression of all mutant and wild type constructs causes a comparable repression of primitive erythropoiesis. Together, our data suggest that a requirement for FOG and its interaction with NuRD during primitive erythropoiesis are conserved in Xenopus and that loss of blood upon FOG overexpression is due to a dominant-interfering effect

Proximity among distant regulatory elements at the β-globin locus requires GATA-1 and FOG-1

Recent evidence suggests that long-range enhancers and gene promoters are in close proximity, which might reflect the formation of chromatin loops. Here, we examined the mechanism for DNA looping at the β-globin locus. By using chromosome conformation capture (3C), we show that the hematopoietic transcription factor GATA-1 and its cofactor FOG-1 are required for the physical interaction between the β-globin locus control region (LCR) and the β-major globin promoter. Kinetic studies reveal that GATA-1-induced loop formation correlates with the onset of β-globin transcription and occurs independently of new protein synthesis. GATA-1 occupies the β-major globin promoter normally in fetal liver erythroblasts from mice lacking the LCR, suggesting that GATA-1 binding to the promoter and LCR are independent events that occur prior to loop formation. Together, these data demonstrate that GATA-1 and FOG-1 are essential anchors for a tissue-specific chromatin loop, providing general insights into long-range enhancer function

GATA-1 associates with and inhibits p53

In addition to orchestrating the expression of all erythroid-specific genes, GATA-1 controls the growth, differentiation, and survival of the erythroid lineage through the regulation of genes that manipulate the cell cycle and apoptosis. The stages of mammalian erythropoiesis include global gene inactivation, nuclear condensation, and enucleation to yield circulating erythrocytes, and some of the genes whose expression are altered by GATA-1 during this process are members of the p53 pathway. In this study, we demonstrate a specific in vitro interaction between the transactivation domain of p53 (p53TAD) and a segment of the GATA-1 DNA-binding domain that includes the carboxyl-terminal zinc-finger domain. We also show by immunoprecipitation that the native GATA-1 and p53 interact in erythroid cells and that activation of p53-responsive promoters in an erythroid cell line can be inhibited by the overexpression of GATA-1. Mutational analysis reveals that GATA-1 inhibition of p53 minimally requires the segment of the GATA-1 DNA-binding domain that interacts with p53TAD. This inhibition is reciprocal, as the activation of a GATA-1–responsive promoter can be inhibited by p53. Based on these findings, we conclude that inhibition of the p53 pathway by GATA-1 may be essential for erythroid cell development and survival