Trans-acting

In the field of molecular biology, trans-acting (trans-regulatory, trans-regulation), in general, means "acting from a different molecule" (i.e., intermolecular). It may be considered the opposite of cis-acting (cis-regulatory, cis-regulation), which, in general, means "acting from the same molecule" (i.e., intramolecular).

In the context of transcription regulation, a trans-acting factor is usually a regulatory protein that binds to DNA.{{cite book

|last1=Brooker

|first1=Robert J

|title=Genetics: analysis and principles

|publisher=McGraw-Hill Education

|location=New York, NY

|edition=6th}} The binding of a trans-acting factor to a cis-regulatory element in DNA can cause changes in transcriptional expression levels. microRNAs or other diffusible molecules are also examples of trans-acting factors that can regulate target sequences.{{cite book

| last = Watson

| first = James D.

|author2=Caudy, Amy A |author3=Myers, Richard M. |author4=Witkowski, Jan A.

| authorlink = James D. Watson

| title = Recombinant DNA: Genes and Genomes - A Short Course

| publisher = Cold Spring Harbor Press

| year = 2007

| pages = 57–58

| isbn = 978-0-7167-2866-5 }}

The trans-acting gene may be on a different chromosome to the target gene, but the activity is via the intermediary protein or RNA that it encodes. Cis-acting elements, on the other hand, do not code for protein or RNA. Both the trans-acting gene and the protein/RNA that it encodes are said to "act in trans" on the target gene.

Transcription factors are categorized as trans-acting factors.