Centromere autoantigens are associated with the nucleolus

Area of Science:

• Cell Biology
• Immunology
• Molecular Biology

Background:

• Scleroderma is characterized by autoantibodies targeting various cellular components.
• Major autoantigens in scleroderma are known to localize to the interphase nucleolus.
• The precise relationship between interphase centromeres and the nucleolus remains unclear.

Purpose of the Study:

• To investigate the potential association between interphase centromeres and the nucleolus.
• To determine if centromeres are integral components of the interphase nucleolus.
• To further understand the localization of scleroderma autoantigens.

Main Methods:

• Indirect immunofluorescence microscopy using human anticentromere autoantibodies (ACA) from scleroderma patients.
• Double-label immunofluorescence with nucleolar proteins (Ki-67, fibrillarin, B23/nucleophosmin).
• Immunoelectron microscopy and nucleolar isolation followed by Western blotting.

Main Results:

• Interphase centromeres exhibited nonrandom clumping suggestive of nucleolar distribution.
• Centromeres were observed around and within nucleoli across various cell types.
• Immunoelectron microscopy confirmed centromeres within the nucleoplasm, near the nuclear envelope, and embedded within nucleoli.
• Actinomycin D treatment dissociated centromeres from segregated nucleoli.
• Centromere autoantigens copurified with isolated nucleoli, indicating association.

Conclusions:

• Interphase centromeres can associate with and potentially be considered part of the interphase nucleolus.
• This finding localizes all major scleroderma autoantigens to the nucleolus, providing new insights into the disease pathogenesis.