HHV latency associated transcript

HHV Infected Cell Polypeptide 0 (ICP0) gene is expressed very early during lytic infection, and for this reason is called an immediate-early Herpes gene. In 1991, Farrell and colleagues reported that the 2.0-kb LAT intron terminates at the 5′ end with a 750-base antisense RNA complement for the ICP0 gene. Chromatin insulator LAT DNA contains an activation boundary between activated LAT-DNA and the inactive lytic viral DNA called a chromatin insulator. CCCTC-binding factor (CTCF) is a zinc finger protein which occurs naturally in some human cells. CTCF is localized to the nucleus of cells. CTCF has been shown A March 2006 University of Florida College of Medicine study showed that expression of the Herpes virus genome may be regulated in part by the binding of CTCF to CTCF-binding motifs. The researchers used sequence analysis and quantitative genomics assays on HHV DNA. In the U. Florida study, the LAT region was found to contain a CTCF-binding region within a 1.5k-bp (base pair) region, and found to contain a "chromatin insulator-like element". == Interference of cellular pathways ==

It was alleged that a portion of HSV-1 LAT consists of an interfering micro RNA (miRNA), termed mir-LAT. This miRNA is shown to downregulate Transforming Growth Factor-β1 (TGF-β1) and SMAD3. These effects block apoptosis, or normal programmed cell death. However, although HSV does downregulate apotopsis, the particular miRNA has come to been seen as an experimental artifact, and the paper was consequently retracted. Other research showed that the products from the first 4,658 nucleotides of LAT inhibited caspase-8 and caspase-9 cellular death factors. == Protein products ==

The exon parts of LAT-DNA produce two protein products with repeats that are 17 amino acids long, termed HHV latency-related proteins or LR-ORF1 and LR-ORF2. Little is known about these two proteins ( and in HHV-1; and in BHV-1), although the loss of ORF2 in bovine herpesvirus-1 (BHV-1) does appear to interfere with the establishment of latency. ORF2 has been shown to possess DNA-binding properties. It appears responsible for the inhibition of apotopsis. == Footnotes ==