Cell-type-specific control elements of the lymphotropic papovavirus enhancer

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Lymphotropic papovavirus (LPV) demonstrates a narrow host range, primarily infecting primate B-lymphocyte cells.
• The virus's enhancer element is crucial for its tropism, directing transcriptional potentiation within the hematopoietic lineage.

Purpose of the Study:

• To investigate the molecular mechanisms underlying LPV's restricted host range.
• To identify protein factors interacting with the LPV enhancer and their role in viral tropism.
• To understand how enhancer activity is regulated during B-cell differentiation.

Main Methods:

• DNase I footprinting and gel retardation assays were used to analyze protein-DNA interactions.
• Nuclear extracts from B cells, T cells, and HeLa cells were employed.
• Functional analysis of enhancer motifs and upstream sequences was performed.

Main Results:

• Nuclear extracts from B and T cells, but not HeLa cells, contain factors that specifically bind the LPV enhancer repeat.
• Three key motifs within the enhancer (core, Pu box, T motif) and upstream sequences contribute to optimal activity.
• Distinct binding patterns of B and T lymphocyte nuclear proteins to the enhancer correlate with differential transcriptional activity.
• LPV enhancer activity and protein interactions are regulated during B-cell differentiation.

Conclusions:

• The LPV enhancer's specific protein interactions in B and T lymphocytes are critical for its host tropism.
• Differential protein binding and enhancer activity in B and T cells contribute to LPV's restricted host range.
• Regulation of LPV enhancer activity during B-cell differentiation suggests a role in viral lifecycle control.