Jodie Laine

Another common technique is poly-A selection. But this only works if you want to study mRNA, as it positively selects for molecules with a poly-A tail (most mRNAs). Since rRNA lacks a poly-A tail, it's left behind. However, this misses non-polyadenylated RNAs (like some lncRNAs and bacterial mRNAs). For total RNA depletion (including non-polyA), the probe-based kits mentioned above are better. For a low-tech, older method, you could use enzymatic digestion with RNase H and specific DNA oligos, but it's fiddly and not as complete as modern kits. The choice really depends on your downstream application and budget. For most next-gen sequencing applications, just go with a reputable depletion kit—it saves a lot of headache.