Searching for Basic Patents ~ Green-fluorescent Protein~

Octorber 13, 2009
Harakenzo World Patent&Trademark
Patent attorney Kenjiro Fujita

Again, the season of the Nobel Prize has come. It is still fresh in your memory that the last year's Nobel Prize in Chemistry was on Aequorea Victoria derived Green-fluorescent Protein (GFP).
Recent development in biotechnological research is outstanding. It is not an overstatement that important results are being announced on minute basis. Back to 1980s to early 1990s, however, a lot of patent applications regarding techniques which now seem ordinary but are in fact significant, were filed and granted patents.
For example, I think that the GFP mentioned above is a quite common technique that every biotechnological researcher has used more than once. Although a number of the GFP related patent applications have been granted patents, it seems that what its basic patents are like is not widely known.

GFP was isolated in 1960s (see document 1), and its gene was isolated in early 1990s (see document 2). Both were published to the public.

Document 1: Shimomura, O., Johnson, F. H., Saiga, Y., (1962) J. Cell. Comp. Physiol., 59:223.
Document 2: Prasher, D. C., Eckenrode, V. K., Ward, W. W., Prendergast, F. G., and Cormier, M. J., (1992), Gene, 111:229.

As far as I know through my searching, there is no effective patent in GFP and gene encoding GFP, while it is well known that a wide variety of modified proteins that are modified from GFP and genes encoding the modified proteins are being developed, and are granted patents. They should be regarded as improved invention of GFP.

Meanwhile, we now see US patent No. 5491084, which still maintains its right. Claim 1 in this literature is as follows;

Claim 1
A host cell comprising a DNA molecule having a regulatory element from a gene, other than a gene encoding an Aequorea victoria green-fluorescent protein operatively linked to a DNA sequence encoding the fluorescent Aequorea victoria green-fluorescent protein.

As such US patent No. 5491084 is directed to "A host cell comprising a DNA molecule having a regulatory element from a gene (a promoter etc., other than a promoter of the GFP gene) linked to an Aequorea victoria GFP gene".

Although the wild-type GFP widely used as a research tool and its gene are not directly protected by patent right, the act of genetic transformation using GFP gene is substantially protected by the above patent in the United States. Currently, GFP is used as a marker within a host cell in most cases. Therefore, I believe that the above US patent can be surely considered as one of the basic patents of GFP.

US patent No. 5491084 was filed on September 10, 1993 (priority date), and at that time GFP gene had already been published (the Document 2). The patent was granted on February 13, 1996 after responding to the Office Action twice. I suppose that the advantages of this invention listed below made the application granted under the difficult circumstances:
1) According to US patent No. 5491084, GFP emits light by artificially excited ultraviolet radiation, not by Aequorin protein which is essential for emitting light within Aequorea Victoria;
2) According to US patent No. 5491084, by utilizing the unique feature of GFP that it emits light without presenting neurotoxic property, it proposed new applications of GFP as a marker; and
3) It succeeded in expression of GFP using two kinds of host cells, which GFP once had been difficult to express using heterologous cells.
Thinking back to recent development in biotechnological research, I found it surprising that US patent No. 5491084, which is apparently a mere invention of expressing the traditional gene using heterologous cells, maintains its patent right even by now, after around forty years has passed since the GFP protein was isolated.

Further, inventors of US patent No. 5491084 also invented the similar invention regarding the expression of cells using modified GFP. The patent application was granted as US patent No. 6146826.