Final answer:
TFIIS is the transcription factor that assists RNA polymerase II in removing incorrectly incorporated nucleotides during eukaryotic transcription.
Step-by-step explanation:
The transcription factor required to aid RNA polymerase in the removal of an incorrect nucleotide incorporated into the growing RNA is TFIIS. In the complex process of eukaryotic transcription, RNA polymerase II relies on various transcription factors to form a pre-initiation complex and initiate transcription. Among these factors, TFIIS plays a specialized role by giving RNA polymerase II the ability to carry out proofreading functions, which includes the removal of incorrect nucleotides that may have been incorporated during RNA synthesis. Although not part of the initial assembly of the transcription initiation complex, TFIIS is essential for RNA polymerase II's error correction capability during the transcription process.