Maxicircleminicircle

Maxicircleminicircle is a term used to describe the two distinct components of kinetoplast DNA (kDNA), the unusual mitochondrial genome found in many kinetoplastid protozoa such as Trypanosoma and Leishmania. The kDNA is organized as a dense network within a single, large mitochondrion, containing both maxi- and minicircles that are interlinked in a single continuous structure.

Maxicircles are the larger circles, typically about 20 to 30 kilobases in length. They encode most of the standard mitochondrial genes, including several subunits of the respiratory complexes and small ribosomal RNA genes. Many of these transcripts, however, are not functional in their initial form and require extensive RNA editing to become translatable. RNA editing in kinetoplastids is guided by small RNAs encoded primarily by minicircles, which provide the templates for inserting or deleting uridines at precise locations.

Minicircles are much smaller, generally around 0.2 to 2.5 kilobases, and exist in thousands of copies that populate the kDNA network. Their primary role is to encode guide RNAs (gRNAs) that direct the editing of maxicircle transcripts. The complete set of gRNAs is necessary to convert pre-edited mRNAs into mature, functional transcripts, enabling the production of essential mitochondrial proteins.

Replication and segregation of the maxicircle and minicircle populations are coordinated within the kinetoplast. After replication, daughter circles are reattached to the network and are distributed to daughter cells during cell division. The kinetoplast DNA arrangement is a characteristic feature of these organisms and has attracted interest as a potential target for antiparasitic strategies, given its essential role in mitochondrial function and RNA editing.