Final answer:
HP1 recruits chromatin-modifying enzymes such as histone acetyltransferases, de-acetylases, and methyltransferases, which are responsible for histone modifications affecting chromatin structure and gene expression. The correct option for proteins recruited by HP1 is option 1). chromatin-modifying enzymes.
Step-by-step explanation:
Once heterochromatin protein 1 (HP1) forms a dimer in the linker region between nucleosomes, it recruits a variety of proteins that facilitate chromatin remodeling and gene regulation. Among these proteins are chromatin-modifying enzymes which include histone acetyltransferases, de-acetylases, and methyltransferases. These enzymes are responsible for adding or removing chemical groups to histones, which can either open up the chromatin to make DNA accessible for transcription or close it to silence genes.
Specific modifications like histone acetylation and methylation play critical roles in regulating gene expression. For instance, acetylation of histones H2B and H4 can unwind nucleosomes, thus enhancing transcription. Conversely, methylation can either activate or repress transcription depending on the residue that is modified. In conclusion, the correct option for the type of proteins recruited by HP1 to the site of dimer formation in the linker region between nucleosomes is chromatin-modifying enzymes. These enzymes catalyze reversible modifications that have significant impacts on chromatin structure, nucleosome spacing, and gene expression. Therefore, the correct option is 1) chromatin-modifying enzymes.