Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report the clinical evaluation of an improved DNA probe assay for the characteristic genetic marker of human CML, observed by cytogenetics and designated the Philadelphia chromosome (Ph1). The Ph1 chromosome results from the fusion of c-abl proto-oncogene sequences from chromosome 9 to phl gene sequence on chromosome 22. (The phl gene is often referred to as bcr. However, for clarity we prefer to reserve the designation "bcr" for the region within the phl gene in which translocation breakpoints have been found to occur. We also find it useful to distinguish between two such regions in phl, bcr-210 and bcr-190, named after the 210- and 190-kDa phl/abl fusion proteins resulting from translocations with breakpoints in the respective regions. We refer to the corresponding chromosomal translocations as Ph1(bcr-210) and Ph1(bcr-190).) DNA, extracted from peripheral blood (PB) or bone marrow (BM) and digested with restriction endonuclease BglII, is hybridized with a probe (phl/bcr-3) spanning a breakpoint cluster region within phl. Rearrangements are revealed by the presence of one or two novel junction fragments. Clinical specimens from leukemic patients with active disease were compared by cytogenetic and DNA probe analysis at seven centers in the United States and Europe. The probe assay identified the phl rearrangement in 190 of 191 cases of Ph1-positive CML, as well as in 12 of 27 clinically diagnosed CML specimens lacking a typical Ph1 chromosome. DNA rearrangements also were seen in two of six cases of Ph1-positive ALL. No false positive results were obtained among 93 non-leukemic controls. Mixing experiments showed that the DNA probe assay can detect as few as 1% leukemic cells in a specimen. A preliminary study of CML patients in remission after allogeneic BM transplantation revealed a small fraction of residual Ph1-positive leukemic cells in a significant number of such patients.
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PMID:Clinical evaluation of a DNA probe assay for the Philadelphia (Ph1) translocation in chronic myelogenous leukemia. 305 Feb 93

The Philadelphia (Ph) translocation [t(9;22)(q34;q11)] is the most common genetic abnormality in human leukemia; a transposition of the ABL gene to the major-breakpoint cluster region (M-BCR) is associated with the pathogenesis in Ph+ chronic myelogenous leukemia (Ph+ CML) and in some cases of Ph+ acute leukemia (Ph+ AL). Our current understanding of the methylation of human genomes allows us to consider the association between the epigenetic phenomenon and the control of differentiation and proliferation in mammalian cells. In order to determine whether the methylation status of the M-BCR is associated with breakpoint-localization in this region and with the lineage of hematopoietic cells, we have examined 28 patients with Ph+ leukemias, including nine with Ph+ AL, six patients with acute myeloblastic leukemia without Ph (Ph- AML), and five patients with Ph- acute lymphoblastic leukemia (Ph- ALL); using the restriction endonuclease isochizomers, MspI and HpaII. In CML patients in the chronic phase, the hypomethylated status within the normal M-BCR allele is heterogeneous. In contrast, patients with Ph+ CML in the lymphoid blast crisis phase exhibited a 2.5/2.7 kb band with a complete disappearance of the germline M-BCR fragment (type L). This pattern is consistently noted in Ph- ALL cells, and the pattern is quite different from that found in myeloid blast crisis or Ph- AML (type M). In patients with M-BCR-nonrearranged Ph+ ALL, it is suggested that the M-BCR methylation patterns are cell-lineage specific but some Ph+ ALL cells had a hypomethylation pattern that was identical to that observed in Ph- AML, suggesting a distinction of genetic diversity of leukemia cells with the Ph chromosome, especially Ph+ AL.
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PMID:The methylation status of the major breakpoint cluster region in human leukemia cells, including Philadelphia chromosome-positive cells, is linked to the lineage of hematopoietic cells. 850 75

Clonal rearrangements of the Ig heavy chain (IGH) locus consisting of either intrachromosomal (VDJ) rearrangements or interchromosomal translocations are a consistent feature of all B-cell malignancies and may be used both diagnostically and to monitor response to therapy. Many of these rearrangements are targeted to the IGHJ segments, but only some can be amplified with regular polymerase chain reaction (PCR) techniques. To permit PCR amplification of potentially all IGHJ rearrangements, we have devised a method incorporating self-ligation of restriction endonuclease-digested DNA fragments with long-distance PCR (long-distance, inverse PCR [LDI-PCR]). We show here, using only 4 nested oligonucleotide primers, the successful amplification and DNA sequencing of all IGHJ rearrangements up to 5.4 kb in length from a panel of 13 cases and cell lines of various types of B-cell malignancy. In all cases, both VDJ and DJ IGH rearrangements and translocation breakpoints were amplified. Six cases exhibited t(14;18)(q32;q21). All translocation breakpoints were cloned and sequenced. Three cases exhibited a rearrangement to the BCL2 major breakpoint region (MBR). However, 2 other cases exhibited rearrangements between the MBR and the minor cluster region (mcr). These 2 cases broke within 44 bp of each other, confirming the presence of an additional 3' BCL2 breakpoint cluster region. The final case fell immediately 3' of the 3' UTR of the BCL2 gene adjacent to an Alu repeat. No other BCL2 breakpoints within this region have been reported. Four cases exhibited t(11;14)(q13;q32). All 3 cases with translocations targeted to the IGHJ segments were successfully amplified and sequenced, including 1 case in which the BCL1 translocation could not be detected by DNA blot using the currently available probes. All three translocation breakpointsfell outside the BCL1 major translocation cluster between 20 and 40 kb telomeric and showed no clustering. Two of the three fell within or adjacent to Alu repeat regions. LDI-PCR is a simple and robust technique that allows PCR amplification of nearly all IGHJ rearrangements.
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PMID:Rapid molecular cloning of rearrangements of the IGHJ locus using long-distance inverse polymerase chain reaction. 931 Apr 98

Co-expression of multiple variants of the MLL/AF4 fusion transcript is a common phenomenon in patients with acute lymphoblastic leukemia (ALL) with t(4;11)(q21;q23). Different transcriptional and post-transcriptional mechanisms were found to contribute to the heterogeneity of the chimeric transcripts. Multiple splice variants are generated by utilizing alternative splice sites that result in the joining of different MLL-exons within the breakpoint cluster region to one of three exons in the AF4 fusion partner. To address the question of how splice site selection occurs during RNA processing, we investigated der(11) transcripts in 10 infants with t(4;11) positive ALL. Specific RT-PCR products were analyzed by Southern blot hybridization, SSCP, endonuclease digestion, cloning and sequencing. In patients co-expressing as many as six different chimeric mRNA species, activation of cryptic splice sites has been detected in MLL-exons 8 and 10. This led to the formation of four novel transcript variants, three of which maintained open reading frames (ORFs). Patients with cryptic donor site activation in MLL-exon 8 did not have any MLL-exon 8/AF4 transcripts using the authentic 5' splice site, although this site is 100% homologous to the consensus sequence. However, since MLL-exon 8 does not end in-phase, the use of the authentic splice site would result in loss of the ORF of the fusion message. The activated cryptic splicing sites are located in the vicinity of the polypurine stretches present in MLL-exons 8 and 10, which are known to function as splicing enhancers recognized by SR proteins. We postulate that both the nonsense-mediated decay eliminating correctly spliced MLL-exon 8/AF4 mRNAs and activation of suboptimal splicing sites contribute to the diversity of MLL/AF4 RNA species.
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PMID:Cryptic splice site activation during RNA processing of MLL/AF4 chimeric transcripts in infants with t(4;11) positive ALL. 1077 50