Catalyzes the ATP-dependent unwinding of RNA duplexes with a single-stranded 3' RNA extension (PubMed:27871484, PubMed:29844170, PubMed:29906447). Central subunit of many protein complexes, namely TRAMP-like, nuclear exosome targeting (NEXT) and poly(A) tail exosome targeting (PAXT) (PubMed:21855801, PubMed:27871484, PubMed:29844170). NEXT functions as an RNA exosome cofactor that directs a subset of non- coding short-lived RNAs for exosomal degradation. NEXT is involved in surveillance and turnover of aberrant transcripts and non-coding RNAs (PubMed:27871484, PubMed:29844170). PAXT directs a subset of long and polyadenylated poly(A) RNAs for exosomal degradation. The RNA exosome is fundamental for the degradation of RNA in eukaryotic nuclei. Substrate targeting is facilitated by its cofactor ZCCHC8, which links to RNA-binding protein adapters (PubMed:27871484). Associated with the RNA exosome complex and involved in the 3'-processing of the 7S pre-RNA to the mature 5.8S rRNA (PubMed:17412707, PubMed:29107693). May be involved in pre-mRNA splicing. In the context of NEXT complex can also in vitro unwind DNA:RNA heteroduplexes with a 3' poly (A) RNA tracking strand (PubMed:29844170). Can promote unwinding and degradation of structured RNA substrates when associated with the nuclear exosome and its cofactors. Can displace a DNA strand while translocating on RNA to ultimately degrade the RNA within a DNA/RNA heteroduplex (PubMed:29906447). Plays a role in DNA damage response (PubMed:29902117). {ECO:0000269|PubMed:17412707, ECO:0000269|PubMed:21855801, ECO:0000269|PubMed:27871484, ECO:0000269|PubMed:29107693, ECO:0000269|PubMed:29844170, ECO:0000269|PubMed:29902117, ECO:0000269|PubMed:29906447}. This is the function of MTREX (Mtr4 exosome RNA helicase, ENSG00000039123).