Constance A. Griffin

Isolation and Characterization of the Human Cytochrome P450 CYP1B1 Gene

Previously, we identified a novel human cytochrome P450 cDNA that is inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and represents the first member of a new subfamily designated cytochrome P4501B1 (CYP1B1; Sutter, T. R., Tang, Y. M., Hayes, C. L., Wo, Y. P., Jabs, E. W., Li, X., Yin, H., Cody, C. W., and Greenlee, W. F. (1994) J. Biol. Chem. 269, 13092-13099). Here, we report on the isolation and initial characterization of the CYP1B1 gene. The CYP1B1 gene maps to human chromosome 2 at 2p21-22 and contains three exons and two introns. The putative open reading frame starts in the second exon and is 1629 base pairs in length. Southern analysis using DNA probes directed to each of the three exons confirmed that CYP1B1 is a single copy gene. Human CYP1B1 differs from its two most closely related members of the cytochrome P450 superfamily, CYP1A1 and CYP1A2, in the number of exons (3 versus 7) and chromosome location (2 versus 15). A single transcription initiation site was identified by primer extension analysis and S1 nuclease mapping. Based on nucleotide sequence analysis, the CYP1B1 gene lacks a consensus TATA box in the promoter region and contains nine TCDD-responsive enhancer core binding motifs (5′-GCGTG-3′) located within a 2.5-kilobase pair genomic fragment 5′-ward of the transcription initiation start site. Deletion analysis of chloramphenicol acetyltransferase reporter gene constructs containing 5′ CYP1B1 genomic fragments indicates that a region from −1022 to −835 containing three of the nine core binding motifs contributes to the TCDD-inducible expression of CYP1B1.

Regional assignment of the gene for human liver/bone/kidney alkaline phosphatase to chromosome 1p36.1-p34.

We have used three different methods to map the human liver/bone/kidney alkaline phosphatase (ALPL) locus: (1) Southern blot analysis of DNA derived from a panel of human-rodent somatic cell hybrids; (2) in situ hybridization to human chromosomes; and (3) genetic linkage analysis. Our results indicate that the ALPL locus maps to human chromosome bands 1p36.1-p34 and is genetically linked to the Rh (maximum lod score of 15.66 at a recombination value of 0.10) and fucosidase A (maximum lod score of 8.24 at a recombination value of 0.02) loci. These results, combined with restriction fragment length polymorphisms identified by ALPL DNA probes, provide a useful marker for gene mapping studies involving the short arm of chromosome 1. In addition, our results help to elucidate further the structure and evolution of the human alkaline phosphatase multigene enzyme family.

Clonal chromosome rearrangements in a uterine myoma

A cytogenetic study of a myoma of uterus with extensive hyaline, myxoid, and cystic degeneration revealed a clonal karyotype with a complex structural rearrangement involving chromosomes #3, #12, #14, #17, and #22. The modal chromosome number of the tumor was 45 due to monosomy #22. Analysis of seven additional myomas of the uterus including five tumors with typical histology and two with degenerative changes showed no clonal abnormalities. Single metaphases with a trisomy and a translocation were detected in two tumors. We conclude that although many uterine myomas appear to have normal karyotypes, clonal chromosome abnormalities are present in some of these tumors.

Cytogenetics and cancer.

Techniques based on fluorescence in situ hybridization (FISH) have bridged the gap between molecular genetics and conventional cytogenetics. Since its introduction in the late 1980s, advanced FISH-based methods have greatly enhanced the cytogenetic analysis of hematopoietic and solid tumors and are rapidly gaining ground in clinical cytogenetic diagnostics. As interest in FISH technologies has grown, it has inspired an era of new FISH-based technologies such as multiplex FISH, spectral karyotyping, and comparative genomic hybridization. In this review, the focus is on the impact of these technologies in the field of cancer genetics.

Human platelet factor 4 gene is mapped to 4q12→q21

The gene for human platelet factor 4 has been mapped to the q12----q21 region of chromosome 4 by in situ hybridization. Hybridization of the same probe to leukemic cells carrying a t(4;11)(q21;q23) showed that the human platelet factor 4 gene is proximal to the breakpoint on chromosome 4.