Cytological Hybridization to Mammalian Chromosomes

As, Henderson

doi:10.1016/s0074-7696(08)61787-8

Cited by 44 publications

(8 citation statements)

References 146 publications

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“…Genes cannot be assigned reliably to a single chromosomal band by in situ hybridization to normal chromosomes, because the silver grains seen after autoradiography are the result of random radioactive disintegrations in three dimen-sions (12). Consequently, we assign the class I Ul pseudogenes to a three-band region, 1q12-q22.…”

Section: Resultsmentioning

confidence: 97%

Human U1 small nuclear RNA pseudogenes do not map to the site of the U1 genes in 1p36 but are clustered in 1q12-q22.

Lindgren¹,

Bernstein²,

Weiner³

et al. 1985

Mol. Cell. Biol.

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Human U1 small nuclear RNA is encoded by approximately 30 gene copies. All of the U1 genes share several kilobases of essentially perfect flanking homology both upstream and downstream from the U1 coding region, but remarkably, for many U1 genes excellent flanking homology extends at least 24 kilobases upstream and 20 kilobases downstream. Class I U1 RNA pseudogenes are abundant in the human genome. These pseudogenes contain a complete but imperfect U1 coding region and possess extensive flanking homology to the true U1 genes. We mapped four class I pseudogenes by in situ hybridization to the long arm of chromosome 1, bands q12-q22, a region distinct from the site on the distal short arm of chromosome 1 to which the U1 genes have been previously mapped (Lund et al., Mol. Cell. Biol. 3:2211-2220, 1983; Naylor et al., Somat. Cell Mol. Genet. 10:307-313, 1984). We confirmed our in situ hybridization results by genomic blotting experiments with somatic cell hybrid lines with translocation products of human chromosome 1. These experiments provide further evidence that class I U1 pseudogenes and the true U1 genes are not interspersed. The results, along with those published elsewhere (Bernstein et al., Mol. Cell. Biol. 5:2159-2171, 1985), suggest that gene amplification may be responsible for the sequence homogeneity of the human U1 gene family.

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Section: Resultsmentioning

confidence: 97%

Human U1 small nuclear RNA pseudogenes do not map to the site of the U1 genes in 1p36 but are clustered in 1q12-q22.

Lindgren¹,

Bernstein²,

Weiner³

et al. 1985

Mol. Cell. Biol.

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“…In most of these experiments we identified all rat chromosomes on the basis of their characteristic G-banding patterns. However, it is known that the G-banding procedure applied before hybridization can lower the hybridization efficiency (21). For this reason, we also analyzed size groups of the chromosomes hybridized to the probes without prior Gbanding (see footnote c, Table 1).…”

mentioning

confidence: 99%

RNA-mediated gene duplication: the rat preproinsulin I gene is a functional retroposon.

Soares¹,

Schon²,

Henderson³

et al. 1985

Mol. Cell. Biol.

229

145

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Rats and mice have two, equally expressed, nonallelic genes encoding preproinsulin (genes I and II). Cytological hybridization with metaphase chromosomes indicated that both genes reside on rat chromosome 1 but are approximately 100,000 kilobases apart. In mice the two genes reside on two different chromosomes.DNA sequence comparisons of the gene-flanking regions in rats and nmice indicated that the preproinsulin gene I has lost one of the two introns present in gene II, is flanked by a long (41-base) direct repeat, and has a remnant of a polydeoxyadenylate acid tract preceding the downstream direct repeat. These structural features indicated that gene I was generated by an RNA-mediated duplication-transposition event involving a transcript of gene II which was initiated upstream from the normal capping site. Sequence divergence analysis indicated that the pair of the original gene and its retroposed, but functional, counterpart (which appeared about 35 million years ago) is maintained by strong negative selection operating primarily on the segments encoding the chains of the mature hormone, whereas the segments encoding the parts of the polypeptide that are eliminated during processing and also the introns and the flanking regions are evolving neutrally.Rats (as well as mice and three fish species) have two insulins instead of one, in contrast to other organisms (13,23). These rat hormones are the products of two nonallelic preproinsulin genes (57) that are almost equally expressed (11). Characterization of the duplicated genes (36), isolated from a rat chromosomal DNA library, indicated a significant structural difference between them. The gene for preproinsulin I has a single 119-base-pair (bp) intron interrupting the segment corresponding to the 5' noncoding region of the mRNA, whereas the other gene, encoding preproinsulin II, contains in addition to this small intron a second 499-bp intron interrupting the segment encoding the C-peptide. Since the structures of the unique chicken (46) and human (2, 62) genes are similar to that of the rat gene II (two introns at corresponding positions) we concluded that the two-intron organization corresponds to that of the common ancestor and that introns can be lost during evolution (46). This conclusion was strengthened by the subsequent determination of the structures of the unique dog (30) and guinea pig (7) preproinsulin genes, which are of the twointron type.Intron loss was subsequently documented in a mouse ot-globin pseudogene (45, 69) and later in other pseudogenes that exhibit clearly the features of processed genes (22; see references 34, 56, and 68 for reviews). These observations raised the possibility that the rat preproinsulin I gene was a * Corresponding author. retroposon (51) that had been generated by an RNAmediated duplication-transposition event but which for some reason remained functional. To examine this possibility we mapped the chromosomal location of the two genes and characterized their flanking regions by DNA sequencing to define the break po...

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“…Slides from PHA-slimulated human periph eral lymphocytes were G-bandcd and photographed by light micro scopy prior to hybridization in situ as described by Henderson (1982). The slides were dcstained in xylene-methanol, washed with 2 x SSC (0.3 M sodium chloride and 0.03 M sodium citrate, pi I 7.1) and then dehydrated in an ethanol series (twice in 70% ethanol for 5 min each: once in 95% ethanol for 5 min).…”

Section: Methodsmentioning

confidence: 99%