title: Upstream conserved sequences of mouse leukemia viruses are important for high transgene expression in lymphoid and hematopoietic cells.
abstract: Highly conserved enhancer sequences located in the upstream part of the long terminal repeat (LTR) of murine leukemia retroviruses (MLV) were reported to compromise viral gene expression in multipotent embryonic cells in vitro and to reduce the likelihood for maintenance of retroviral gene expression in hematopoietic cells in vivo. We show that deletion of these sequences (nucleotides +37 to +95) attenuates rather than increases the transcriptional activity of retroviral vectors in hematopoietic cells almost independently of the developmental lineage (erythroid, myeloid, or lymphoid). Expression rates of modified vectors were reduced by as much as 34-65%, although the strong enhancer array located in the direct repeat of the LTR was preserved. Sequence analysis and electrophoretic mobility shift assays revealed the presence of a highly conserved binding site for NFAT (nuclear factor of activated T cells) proteins that immediately neighbors a known binding site for the transcription factor Yin-Yang1 (YY1) [corrected]. Specific inactivation of the NFAT site reduced transgene expression in all cell types investigated and had a similar effect as the destruction of a neighboring SP1 motif. Combined destruction of individual motifs for NFAT, SP1, and E twenty-six transcription factors (ETS) resulted in a severe attenuation (by 40-60%) of the retroviral enhancer. These results provide novel clues for the manipulation of retrovirus replication and vector tropism.
authors.affiliation: Heinrich-Pette-Institute, Department of Cell and Virus Genetics, 20251 Hamburg, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Wahlers
authors.forename: Olga
authors.initials: O
authors.lastname: Kustikova
authors.forename: Peter F
authors.initials: PF
authors.lastname: Zipfel
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Itoh
authors.forename: Markus
authors.initials: M
authors.lastname: Koester
authors.forename: Christoph
authors.initials: C
authors.lastname: Heberlein
authors.forename: Zhixiong
authors.initials: Z
authors.lastname: Li
authors.forename: Bernd
authors.initials: B
authors.lastname: Schiedlmeier
authors.forename: Christine
authors.initials: C
authors.lastname: Skerka
authors.forename: Boris
authors.initials: B
authors.lastname: Fehse
authors.forename: Christopher
authors.initials: C
authors.lastname: Baum
mesh_terms: D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005347:Fibroblasts / Q000502:physiology; D005822:Genetic Vectors; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D009052:Leukemia Virus, Murine; D008214:Lymphocytes / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D012190:Retroviridae / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D019076:Transgenes / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors