Pattern of Expression of Cyclin T1 in Human Tissues

Abstract

S U M M A R Y Cyclin T1 was recently identified, together with cdk9 (previously named PI-TALRE), as part of the TAK multiprotein complex, a co-factor targeted by the human immunodeficiency virus Type 1 (HIV-1) protein named Tat, suggesting a role for this complex in transcription elongation. Although studies on mRNA and protein expression have shown that cyclin T1 is ubiquitous in adult human tissues, no data have yet been reported regarding the expression of this protein in different cell lineages. Using a polyclonal antiserum raised against cyclin T1, we investigated the pattern of expression of this protein in adult human tissues by immunohistochemistry. Cyclin T1 was expressed ubiquitously, although different levels of expression were found in various organs. Some specialized tissues, such as blood, lymphoid tissues, and cells of connective tissue origin, showed high cyclin T1 expression. These specific expression patterns are only partially justified by some well-known specialized functions of cyclin T1 in certain cell types, such as its involvement in peripheral blood lymphocytes and monocyte differentiation. The high expression level found in other tissues suggests new possible roles for cyclin T1 in cell types other than those of lymphoid tissue. (J Histochem Cytochem 49:685-692)

Cyclin T: Three forms for different roles in physiological and pathological functions

“…Finally, immunohistochemical analysis of cyclin T2a expression in a large human tissue bank shows that cyclin T2a is widely expressed in all cell types, even if higher levels are found in some terminally differentiated tissues such as muscle, blood, lymphoid tissue, and connective cells (De Luca et al, 2001a). This expression pattern is very similar to that described above for cyclin T1 (De Luca et al, 2001b) and in agreement with mRNA distribution for cyclin T2a (Peng et al, 1998b).…”

“…Cyclins T2a and T2b share the first 642 amino acids but had different carboxyl termini. Hybridization of the cyclin T2a cDNA probe to human chromosomes shows specific labeling on chromosome 2q21 (De Luca et al, 2001a). …”

Increased cyclin T1 expression as a favorable prognostic factor in treating gastric adenocarcinoma

“…Patterns of CDK9 and cyclin T1 expression were observed to be similar in normal organ tissue, yet quite different in other tissues (5). Cyclin T1 was expressed in a wide variety of human tissues.…”

“…Regulation of the CDK9/cyclin T1 complex depends on its tissue-specific signaling pathway (23) and its response to cytokines including tumor necrosis factor and interleukin-6 (5,24). Deregulated CDK9-related pathways were observed in several human tumors including lymphoma (23,25,26), neuroblastoma (27), Table VII.…”

“…In general, CDK9 consists of a complex of T1, T2a and T2b at ratios of ~80%, 10% and 10%, respectively (3)(4)(5). The expression pattern of cyclin T2a almost completely overlaps the pattern described for cyclin T1 (5). The expression of cyclin T1 increases CDK9 activity and the phosphorylation of RNA polymerase II (RNAPII).…”