ABSTRACT
BACKGROUND: Desmoplastic malignant melanoma (DM) is a rare variant of melanoma. BRAF gene mutations have been poorly explored in this entity. OBJECTIVE: To detect BRAF gene mutation in a series of DM. METHODS: This is a single-center retrospective study of ten patients with DM, with a biomolecular analysis of BRAF mutation. RESULTS: The male:female ratio was 2.3:1, with a mean patient age of 66.5 years. Melanoma arose in the head and neck region in 3 cases. The mean tumor thickness was 7.97 mm, Clark level was IV or V in all cases. Six melanomas were of the pure DM variant. Three patients had at least one local recurrence, two had regional node metastases, and two experienced systemic metastases which they died of (average follow-up 34.1 months). A V600E BRAF mutation was detected in only one patient. CONCLUSION: BRAF mutation seems to be a rare event in DM contrary to other melanoma variants.
Subject(s)
Melanoma/genetics , Mutation , Proto-Oncogene Proteins B-raf/genetics , Skin Neoplasms/genetics , Adolescent , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Retrospective Studies , Young AdultABSTRACT
The interrelationships between proteasomes and viral gene products are very complex. 20S proteasomes associate with a number of viral mRNAs which are cleaved by proteasome's associated endonuclease activity. In addition proteasome's endopeptidase activities are involved in the presentation of viral antigens. Viral proteins of different origin associate with the 20S and 26S complexes and interfere with their enzymatic activities. A major part of this review deals with the interactions between 20S proteasomes and the gene products of the human immunodeficiency virus (HIV) which has been studied in detail by our group.
Subject(s)
Cysteine Endopeptidases/metabolism , Multienzyme Complexes/metabolism , RNA, Viral/metabolism , Viral Proteins/metabolism , Adenosine Triphosphatases/metabolism , HIV/metabolism , HIV Long Terminal Repeat , Humans , Proteasome Endopeptidase Complex , RNA, Messenger/metabolism , RNA, Transfer, Amino Acyl/metabolismABSTRACT
We have identified a cellular target for proteasomal endonuclease activity. Thus, 20 S proteasomes interact with the 3'-untranslated region of certain cytoplasmic mRNAs in vivo, and 20 S proteasomes isolated from Friend leukemia virus-infected mouse spleen cells were found to be associated with a mRNA fragment showing great homology to the 3'-untranslated region of tumor necrosis factor-beta mRNA that contains AUUUA sequences. We furthermore demonstrate that 20 S proteasomes destabilize oligoribonucleotides corresponding to the 3'-untranslated region of tumor necrosis factor-alpha, creating a specific cleavage pattern. The cleavage reaction is accelerated with increasing number of AUUUA motifs, and major cleavage sites are localized at the 5' side of the A residues. These results strongly suggest that 20 S proteasomes could be involved in the destabilization of cytokine mRNAs such as tumor necrosis factor mRNAs and other short-lived mRNAs containing AUUUA sequences.
Subject(s)
Cysteine Endopeptidases/metabolism , Multienzyme Complexes/metabolism , RNA, Messenger/metabolism , 3' Untranslated Regions , Animals , Base Sequence , Cattle , Hydrolysis , Mice , Molecular Sequence Data , Proteasome Endopeptidase Complex , RNA, Messenger/genetics , Ribonucleases/metabolism , Sequence Homology, Nucleic Acid , Tumor Cells, Cultured , Tumor Necrosis Factor-alpha/geneticsABSTRACT
We have identified two distinct subunits of 20 S proteasomes that are associated with RNase activity. Proteasome subunits zeta and iota, eluted from two-dimensional Western blots, hydrolysed tobacco mosaic virus RNA, whereas none of the other subunits degraded this substrate under the same conditions. Additionally, proteasomes were dissociated by 6 M urea, and subunit zeta, containing the highest RNase activity, was isolated by anion-exchange chromatography and gel filtration. Purified subunit zeta migrated as a single spot on two-dimensional PAGE with a molecular mass of approx. 28 kDa. Addition of anti-(subunit zeta) antibodies led to the co-precipitation of this proteasome subunit and nuclease activity. This is the first evidence that proteasomal alpha-type subunits are associated with an enzymic activity, and our results provide further evidence that proteasomes may be involved in cellular RNA metabolism.
Subject(s)
Cysteine Endopeptidases/metabolism , Multienzyme Complexes/metabolism , RNA, Viral/metabolism , Animals , Cattle , Cysteine Endopeptidases/isolation & purification , Hydrolysis , Liver/enzymology , Multienzyme Complexes/isolation & purification , Proteasome Endopeptidase Complex , Ribonucleases/metabolism , Tobacco Mosaic Virus/geneticsABSTRACT
The 20S proteasome (prosome) is a highly organized multiprotein complex with approximate molecular weight of about 700 kDa. Whilst the role of the proteasome in the processing and turnover of cellular proteins is becoming clearer, its relationship with RNA remains still obscure. Here we focus on the nature and function of proteasome associated endonuclease activity. Thus the involvement of a proteasome alpha-type subunit in RNA-degradation, the catalytic requirements, the interaction of proteasomes with their RNA-substrate and the identification of a well defined cleavage site in the 3'UTR of short-lived cellular mRNAs will be described in detail. All data indicate that proteasomes associated endonuclease activity could be involved in post-transcriptional gene control at the level of translation.
