Safer, silencing-resistant lentiviral vectors: optimization of the ubiquitous chromatin-opening element through elimination of aberrant splicing.
Gammaretroviral and lentiviral vectors have been used successfully in several clinical gene therapy trials, although powerful enhancer elements have caused insertional mutagenesis and clonal dysregulation. Self-inactivating vectors with internal heterologous regulatory elements have been developed as potentially safer and more effective alternatives. Lentiviral vectors containing a ubiquitous chromatin opening element from the human HNRPA2B1-CBX3 locus (A2UCOE), which allows position-independent, long-term transgene expression, are particularly promising. In a recently described assay, aberrantly spliced mRNA transcripts initiated in the vector A2UCOE sequence were found to lead to upregulation of growth hormone receptor gene (Ghr) expression in transduced murine Bcl-15 cells. Aberrant hybrid mRNA species formed between A2UCOE and a number of other cellular genes were also detected in transduced human PLB-985 myelomonocytic cells. Modification of the A2UCOE by mutation or deletion of recognized and potential cryptic splice donor sites was able to abrogate these splicing events and hybrid mRNA formation in Bcl-15 cells. This modification did not compromise A2UCOE regulatory activity in terms of resistance to CpG methylation and gene silencing in murine P19 embryonic carcinoma cells. These refined A2UCOE regulatory elements are likely to improve intrinsic biosafety and may be particularly useful for a number of clinical applications where robust gene expression is desirable.
MRC/UCL Centre for Medical Molecular Virology and Wohl Virion Centre, Division of Infection & Immunity, UCL Cancer Institute, University College London, London, United Kingdom.
Sean
S
Knight
Fang
F
Zhang
Uta
U
Mueller-Kuller
Marieke
M
Bokhoven
Abhinav
A
Gupta
Thomas
T
Broughton
Sha
S
Sha
Michael N
MN
Antoniou
Christian
C
Brendel
Manuel
M
Grez
Adrian J
AJ
Thrasher
Mary
M
Collins
Yasuhiro
Y
Takeuchi
D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000235:genetics* / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics; D020868:Gene Silencing; D015316:Genetic Therapy / Q000295:instrumentation; D005822:Genetic Vectors / Q000235:genetics* / Q000378:metabolism; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics; D006801:Humans; D016086:Lentivirus / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D016254:Mutagenesis, Insertional; D012326:RNA Splicing
C518294:CBX3 protein, human; C453799:Cbx3 protein, mouse; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; C439768:hnRNP A2