B Lineage—Specific Interactions of an Immunoglobulin Enhancer with Cellular Factors in Vivo

TLDR

The mouse immunoglobulin heavy chain locus harbors a tissue‑specific enhancer. In vivo dimethyl sulfate protection assays combined with genomic sequencing were used to probe the enhancer and its flanking sequences. Dimethyl sulfate protection revealed B‑cell–specific changes in guanine reactivity within four octamer‑like clusters of the enhancer, indicating lineage‑specific binding of regulatory proteins.

Abstract

The mouse heavy chain immunoglobulin gene contains a tissue-specific enhancer. The enhancer and flanking sequences were studied in vivo by carrying out dimethyl sulfate protection experiments on living cells, in combination with genomic sequencing. Relative to reactions on naked DNA, there are changes (protections and enhancements) in the reactivity of guanine residues to dimethyl sulfate within the enhancer sequence in myeloma, B, and early B cells, whereas virtually no alterations appear in cells of non-B lineage. Most of the affected residues are in four clusters, in sequences homologous to the octamer 5′CAGGTGGC 3′ (C, cytosine; A, adenine; G. guanine; T, thymine). The alterations in the pattern of G reactivity are consistent with the tissue-specific binding of molecules to the mouse immunoglobulin heavy chain enhancer.