Which of the following is NOT one of the four major ways that activator proteins alter chromatin?

The process of histone acetylation, which is the addition of acetyl groups to histone proteins, is indeed a critical mechanism by which activator proteins influence chromatin structure. This modification typically reduces the positive charge on histones, decreasing their affinity for negatively charged DNA, and thereby facilitates a more open and accessible chromatin configuration that promotes gene expression.

On the other hand, nucleosome sliding, nucleosome removal, and histone exchange are distinct and established ways in which activator proteins directly alter chromatin structure to enhance transcription. Nucleosome sliding allows for repositioning of nucleosomes, making DNA more accessible to transcription machinery. Nucleosome removal refers to the displacement of nucleosomes from specific regions of the DNA, creating open chromatin that is conducive to transcription. Histone exchange involves the replacement of existing histones with variants that may have different functional properties, also contributing to the modulation of chromatin structure and gene accessibility.

Since histone acetylation is a well-documented mechanism of chromatin alteration by activator proteins, it is not accurate to classify it as not one of the major ways in which these proteins influence chromatin. Thus, the choice that is not recognized as a primary method in the context of chromatin