Which factor is responsible for recruiting the splicing machinery during RNA processing?

The factor responsible for recruiting the splicing machinery during RNA processing is U2AF65. This protein plays a crucial role in recognizing and assembling the spliceosome complex at the intron-exon boundaries. Specifically, U2AF65 binds to the polypyrimidine tract located near the 3' splice site of pre-mRNA, which is essential for accurate splicing. By doing so, it facilitates the recruitment of other splicing factors and components necessary for the spliceosome's formation and function, leading to the correct splicing of introns from pre-mRNA.

In the context of the other choices, the polyadenylation enzyme is involved in adding a poly(A) tail to the 3' end of mRNA, which affects mRNA stability and translation but does not directly recruit splicing factors. The capping enzyme is responsible for adding a 5' cap to the mRNA, enhancing stability and translation as well, but it does not play a direct role in recruiting splicing machinery. TATSF1, while involved in transcription and other processes, is not directly associated with the recruitment of the splicing machinery either. Thus, U2AF65 is the key player in facilitating the splicing process in RNA processing.