Supplementary Material for: The cHS4 Chromatin Insulator Reduces the Rate of Retroviral Vector-Mediated Gene Dysregulation Associated with Aberrant Vector Transcription

Integrating gammaretroviral vectors can dysregulate the expression of
cellular genes through a variety of mechanisms, leading to genotoxicity
and malignant transformation. Although most attention has focused on
the activation of cellular genes by vector enhancers, aberrant fusion
transcripts involving cellular gene sequences and vector promoters,
vector splice elements, and vector transcription termination sequences
have also been mechanistically associated with dysregulated expression
of cellular genes. Chromatin insulators have emerged as an effective
tool for reducing the frequency of vector-mediated genotoxicity and
malignant transformation and have been shown to block the activation of
cellular genes by vector enhancers. We report here evidence that
flanking a gammaretroviral reporter vector with the cHS4 chromatin
insulator also reduces the frequency of vector-mediated cellular gene
dysregulation associated with aberrant vector transcripts, including
vector transcription run-through and aberrant splicing. We demonstrate
that the cHS4 element does not function to terminate transcription
directly, implicating other mechanisms for this activity.