Final answer:
TAF3 cannot substitute for CTCF as they have distinct functions and are not interchangeable in their roles related to chromatin structure and gene expression.
Step-by-step explanation:
The question asks whether TAF3 can substitute for CTCF, a protein known for its role in organizing the 3D structure of chromatin in the cell nucleus. CTCF is crucial for the formation of chromatin loops and domains, which is vital for the regulation of gene expression. TAF3, a subunit of the TFIID complex, plays a different role primarily in the initiation of transcription by RNA polymerase II.
Research has shown that TAF3 and CTCF have distinct functions and are not interchangeable. TAF3 does not have the zinc finger domains that CTCF has, which are essential for CTCF's interaction with DNA and its insulator function. Therefore, it is true that TAF3 cannot substitute for CTCF. They have different roles in chromatin organization and gene expression.