Human fetal gγ- and Aγ-globin genes: Complete nucleotide sequences suggest that DNA can be exchanged between these duplicated genes

A recombinant phage that carries the cytoplasmic beta-actin gene was isolated from a human DNA library. The nucleotide sequence of this gene was determined. The amino acid sequence deduced from the nucleotide sequence matches perfectly that of beta-actin from human fibroblasts. The gene contains five introns. A large intron was found in the 5' untranslated region six nucleotides upstream from the ATG initiation codon. Four introns were found within the coding region at codons specifying amino acids 41/42, 121/122, 267, and 327/328. In contrast to the human cardiac muscle actin gene, the aorta-type smooth muscle actin gene, and the stomach-type smooth muscle actin gene, the beta-actin gene lacks the codon for cysteine between the ATG initiation codon and the codon for the NH2-terminal amino acid of the mature protein. Hybridization of genomic DNA with DNA fragments derived from intron I in the 5' untranslated region and from intron III strongly suggests the presence of a single beta-actin gene in the human genome. The DNA sequences of the coding region, of the 3' untranslated region, and of the sequence block between the "CCAAT" box and "TATA" box in the 5' flanking DNA of the human beta-actin gene are highly homologous to the corresponding sequences of the rat and chicken beta-actin genes. Unexpectedly, the sequence of intron III of the human beta-actin gene shows considerable homology to that of the rat beta-actin gene.

Molecular structure of the human cytoplasmic beta-actin gene: interspecies homology of sequences in the introns.

Publisher Summary This chapter discusses the structure and organization of mammalian, highly repeated sequences at the molecular level. There is a description of tandemly repeated sequences, that are, satellites, and the segments that are interspersed among other genomic DNA sequences. The methods for the analysis of repeated DNA sequences are measurement of DNA renaturation kinetics and isopycnic centrifugation in gradients of CsCl and CsSO4. Eukaryote genomes can be divided into classes of DNA sequences according to the reiteration frequency. Many highly repeated sequences are in long tandem arrays. Some repetitive sequences are dispersed throughout major portions of genomes amid either other repeated sequences or sequences present only once per genome, that are, uniquesequences. The characteristic organizational feature of satellites and cryptic satellites is the tandem repetition of a unit DNA sequence. Satellite arrays resist separation by isopycnic centrifugation and instead remain within the main density fraction of genomic DNA. The repeat unit and its tandem organization can be revealed by restriction endonuclease digestion.

Highly repeated sequences in mammalian genomes.

The human insulin gene contains two intervening sequences, one is within the region transcribed into the 5'-untranslated segment of the mRNA and the other interrupts the C-peptide encoding region. A comparison of the human with the rat insulin genes indicates potential regulatory regions in the DNA segment preceding the gene and suggests that the ancestral form of the insulin gene had two intervening sequences.

Sequence of the human insulin gene

The structure and evolution of the two nonallelic rat preproinsulin genes

Cloned β-globin genes of both mouse and rabbit each contain a large and a small intervening sequence (intron) of about equal length at precisely the same positions relative to the coding sequence The homologous introns show some sequence similarity, particularly at the junctions with the coding sequence They most probably arose from a common ancestral sequence and diverged substantially during evolution

Comparison of cloned rabbit and mouse beta-globin genes showing strong evolutionary divergence of two homologous pairs of introns.

Localization of repetitive and unique DNA sequences neighbouring the rabbit β-globin gene☆

Physical mapping of repetitive DNA sequences neighboring the rabbit beta-globin gene.

The rabbit and human 	
β-related
globin genes have been analysed using
genomic 'Southern blotting' and molecular
cloning. The rabbit 	
β-globin gene structure
has been worked out in detail and its transcripts
have been characterized by S₁ nuclease
transcription mapping.
The arrangement of the human γδβ-globin
gene locus has been largely elucidated. The
gene order is (5' to 3') GγAγδβ and the
intergene distances are Gγ-Aγ, 3.5 kb; Aγ-δ,
13.5 kb; δ-β, about 6 kb. All these 	
β-related
globin genes are transcribed from
the same DNA strand. Several abnormal globin
genes have been characterized by the same
methods. Thus, δβ°-thalassaemia is the result
of a deletion which begins approximately in
the δ-globin gene large intron and extends
beyond the 	
β-globin gene. A form of 	
β°-thalassaemia
has been mapped where a 600 by
deletion, including the 3' exon of the 	
β-globin gene, has occurred.

/pdf/the-structure-and-expression-of-globin-genes-in-rabbit-and-4y3azpjrvw.pdf

The structure and expression of globin genes in rabbit and man

Publisher Summary This chapter focuses on the structure and expression of normal and abnormal globin genes. Most mammalian genes are present as a single copy per haploid genome and, hence, comprise only about one part in 106 of the total nuclear DNA. This fact impeded work on single-copy genes, but recently recombinant DNA technology and sensitive gene mapping has led to the elucidation of the structure of a number of eukaryotic genes. The chapter examines the structure of the rabbit β-globin gene. The initial approach was to construct a detailed physical map of the rabbit β-globin gene using the blotting-filter hybridization approach. This showed that the β-globin gene consists of at least two noncontiguous blocks of coding sequences separated by an intervening sequence (IVS) of 600 base pairs (bp). The experiments showed that two intervening sequences are present in the rabbit β-globin gene, one of 126 bp in length in length present between the DNA sequences for amino acid 30 and 31 and the one already mentioned above of 573 bp long, present between the sequences coding for amino acids 104 and 105.

/pdf/the-structure-and-expression-of-normal-and-abnormal-globin-5ah4xmyghx.pdf

G.C. Grosveld

Papers

Comparison of cloned rabbit and mouse beta-globin genes showing strong evolutionary divergence of two homologous pairs of introns.

Localization of repetitive and unique DNA sequences neighbouring the rabbit β-globin gene☆

Physical mapping of repetitive DNA sequences neighboring the rabbit beta-globin gene.

The structure and expression of globin genes in rabbit and man

The structure and expression of normal and abnormal globin genes