Role of the duplicated CCAAT box region in gamma-globin gene regulation and hereditary persistence of fetal haemoglobin.

Abstract

Hereditary persistence of fetal haemoglobin (HPFH) is a clinically important condition in which a change in the developmental specificity of the gamma‐globin genes results in varying levels of expression of fetal haemoglobin in the adult. The condition is benign and can significantly alleviate the symptoms of thalassaemia or sickle cell anaemia when co‐inherited with these disorders. We have examined structure‐function relationships in the −117 HPFH gamma promoter by analysing the effect of mutating specific promoter elements on the functioning of the wild‐type and HPFH promoters. We find that CCAAT box mutants dramatically affect expression from the HPFH promoter in adult blood but have little effect on embryonic/fetal expression from the wild‐type promoter. Our results suggest that there are substantial differences in the structure of the wild‐type gamma promoter expressed early in development and the adult HPFH promoter. Together with previous results, this suggests that gamma silencing is a complex multifactorial phenomenon rather than being the result of a simple repressor binding to the promoter. We present a model for gamma‐globin gene silencing that has significant implications for attempts to reactivate the gamma promoters in human adults by pharmacological means.

Role of NF-Y in In Vivo Regulation of the γ-Globin Gene

“…In addition, gel shift assays have shown that GATA-1 binds weakly to the duplicated CCAAT box region (3,15,21). A suggestion that GATA-1 binding to the duplicated CCAAT box region functions as ␥ gene repressor (3,21) was not supported by later experiments (29). It is possible that NF-Y and GATA-1 bind competitively to the duplicated CCAAT box region and that the mutation of the two CCAAT motifs, by severely impairing the binding of NF-Y, increases the probability of binding of GATA-1 to this region.…”

Regulation of the Globin Genes

“…Two more factors are known to influence the expression of the ␥-globin gene and may have a role in Hb switching. One is COUP-TFII (44), a retinoic acid orphan receptor that corresponds to the erythroid specific binding activity of NF-E3 (45,46). The protein binds to a consensus site that includes the ␥-globin CAAT element and may act as a repressor of the ␥-globin expression (47).…”

Regulation of the amylolytic and (hemi-)cellulolytic genes in aspergilli

“…In filamentous fungi, the CCAAT sequence is also shown to modulate the expression of many genes, such as the A. nidulans acetamidase gene (amdS) (Littlejohn and Hynes, 1992), the A. oryzae Taka-amylase A gene (taa) (Nagata et al, 1993), the A. nidulans penicillin biosynthesis gene (ipnA and aatA) , and the Neurospora crassa NADP-specific glutamate dehydrogenase gene (am) (Frederick and Kinsey, 1990) (Table 2). In higher eukaryotes, all kinds of promoters have the CCAAT sequence: developmentally controlled and tissue-specific genes (Berry et al, 1992;Ronchi et al, 1996), housekeeping and inducible genes (Marziali et al, 1997;Roy and Lee, 1995), and cell-cycle regulated genes (Mantovani, 1998).…”