Kamel Ben-Mahrez

Detection of circulating antibodies against c-myc protein in cancer patient sera.

We have partially purified an archaebacterial protein of 84 kD which shares common epitopes with the human c-myc protein as shown by its cross-reactivity with a commercialized anti-human c-myc antiserum. An antiserum raised against the 84 kD protein recognizes a 60 kD protein from HL-60 nuclei. This protein is also recognized by the anti-human c-myc antiserum. Using this archaebacterial protein as antigen for Western blot analysis, we found that the human c-myc oncogene product could be immunogenic and that it is possible, in some spontaneously occurring human tumours, to detect antibodies against the c-myc gene product in the serum of cancer patients.

Stimulation of an alpha like DNA polymerase by v-myc related protein of Halobacterium halobium.

Partial DNA sequencing of a genomic clone of the archaebacterium Halobacterium halobium, which hydridized with an avian v-myc probe, showed especially the presence, in the organism of one of the conserved regions through myb, myc and adenovirus E1a oncogenes. The archaebacterial deduced amino acid sequence displayed significant homology with the v-myc gene product. In accordance with the partial DNA sequencing which assured a sufficient homology to have similar epitopes, a protein having a molecular weight of 70,000 and possessing high antigenicity with a polyclonal antiserum against avian v-myc protein was isolated and purified from H. halobium extracts. The purified v-myc like protein stimulated in vitro DNA synthesis carried out by the alpha like DNA polymerase of H. halobium.

An Archaebacterial Antigen Used to Study Immunological Humoral Response to C-Myc Oncogene Product

We have previously shown that it is possible to detect by Western blot analysis antibodies against the hyman c-niyc oncogene product in the serum of some cancer patients using as antigen an 84 kD protein obtained from Halohacterium halobium [1]. To study whether the presence of circulating anti-c-mvc antibodies might be more strongly associated with a specific type of cancer, sera of 28 colorectal cancer patients at the beginning of their treatment at the “Institut Curie” were tested. We observed a significantly higher level of positivity (18 out of 28) than in other cancer patient sera.

DNA replication in the halophilic archaeobacterium Haloferax volcanii in the absence of protein synthesis

In Haloferax volcanii, DNA replication is not arrested in the absence of protein synthesis. This DNA replication occurs either in complete medium during the inhibition of protein synthesis by anisomycin or in minimal medium during amino acid starvation of an auxotrophic mutant his-1. Once established, this DNA synthesis is permanent. It is also sensitive to aphidicolin, an inhibitor of eukaryotic chromosomal DNA replication. The entire chromosome seems to participate in this replication whereas the synthesis of the resident pHV2 plasmid is reversibly inhibited.

Enzymology and Genetics of an Alpha-Like DNA Polymerase from Halobacterium Halobium

Two DNA polymerases have been isolated from extracts of Halobacterium halobium, one having a sedimentation coefficient of 11 S, designated as alpha-like polymerase and possessing the following characteristics. It is sensitive to both aphidicolin and N-ethylmaleimide but indifferent to the presence of a dideoxynucleoside triphosphate. Therefore this polymerase is very similar to the alpha DNA polymerase of eukaryotes. The enzyme requires 5 M NaCl for maximum activity. The other polymerase has a sedimentation coefficient of 4.4 S and is resistant to both aphidicolin and N-ethylmaleimide. However, it is inhibited by a dideoxynucleoside triphosphate.

A protein of Halobacterium halobium immunologically related to the v-myc gene product

A 70 kDa protein of Halobacterium halobium cross‐reacts with an antiserum directed against the v‐myc gene product of the avian myelocytomatosis virus (MC29). This cross‐reaction is in agreement with hybridization studies which indicate that H. halobium possesses DNA and RNA sequences homologous to the v‐myc gene.