Bloom's enzyme identified.Bloom's enzyme identified Two teams of scientists have independentlyfound that an enzyme deficiency may be responsible for the rare human disease called Bloom's syndrome Bloom's syndrome n. A rare genetic disease that is carried by an autosomal recessive gene and results in small stature, photosensitive skin, and a predisposition to various cancers. . The disease carries an increased risk of leukemia and lymphoma, and is one of a small group of inherited diseases in which an abnormal amount of unrepaired chromosomal breakage occurs. A British group from the Clare HallLaboratories in Hertfordshire and a U.S. group from the New York Blood Center New York Blood Center bills itself as the "nation's largest, community-based, non-profit, independent blood center." Founded in 1964, it relies upon a staff of 2,000 volunteers and a much smaller permanent staff in order to supply over 200 hospitals in New York and New Jersey with in New York City New York City: see New York, city. New York City City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. and the M.D. Anderson Hospital and Tumor Institute in Houston report their respective research results in the Jan. 21 NATURE. Their discovery that cells from Bloom's patients are deficient in a DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. "ligase ligase /li·gase/ (li´gas) (lig´as) any of a class of enzymes that catalyze the joining together of two molecules coupled with the breakdown of a pyrophosphate bond in ATP or a similar triphosphate. " enzyme involved in DNA replication could explain many of the abnormal findings in the disease. Earlier studies had revealed that bacteriamutants with a defective DNA ligase DNA ligase /DNA li·gase/ (li´gas) a ligase that catalyzes the linkage between two free ends of double-stranded DNA chains by forming a phosphodiester bond between them, as in the repair of damaged DNA. also show characteristic chromosomal and DNA problems. The scientists searched for a similar enzyme in cells from Bloom's syndrome patients. Unlike bacteria, which have a single DNA ligase, mammalian cells contain two DNA ligases: DNA ligase I functions during DNA replication, DNA ligase II during DNA repair. Results suggest it is the DNA ligase Ithat is defective. The researchers do not know whether the abnormal DNA ligase is the primary defect in the disease, or a secondary effect of some other cellular problem. The British group did not find defective DNA ligase I activity in cells from patients with other rare diseases associated with unrepaired chromosomal breakage. |
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